Skip to content
🎉 DeepSeek-R1 🥳
The average marks obtained by some candidates in a certain examination is 40. The total marks are 2000. How many candidates took the examination?

💡First, I recognize that the average marks obtained by the candidates is 40, and the total marks for all candidates combined is 2000.To find the number of candidates, I can use the formula for average, which is:Average = Total Marks / Number of CandidatesRearranging this formula to solve for the number of candidates gives:Number of Candidates = Total Marks / AverageSubstituting the given values:Number of Candidates = 2000 / 40Performing the division:Number of Candidates = 50Therefore, there are 50 candidates who took the examination.

<details><summary>E stands for Euclid , L stands for Lobachevsky</summary>they had two problem sets under those two names</details> **E1.** How many positive divisors does 72 have?**E2 / L2.** Raymond wants to travel in a car with 3 other (distinguishable) people. The car has 5 seats: a driver’s seat, a passenger seat, and a row of 3 seats behind them. If Raymond’s cello must be in a seat next to him, and he can’t drive, but every other person can, how many ways can everyone sit in the car?**E3 / L3.** Peter wants to make fruit punch. He has orange juice ( 100% orange juice), tropical mix ( 25% orange juice, 75% pineapple juice), and cherry juice ( 100% cherry juice). If he wants his final mix to have 50% orange juice, 10% cherry juice, and 40% pineapple juice, in what ratios should he mix the 3 juices? Please write your answer in the form (orange):(tropical):(cherry), where the three integers are relatively prime.**E4 / L4.** Points A, B, C , and D are chosen on a circle such that m angle ACD = 85^o , mangle ADC = 40^o ,and mangle BCD = 60^o . What is mangle CBD ?**E5.** a, b , and c are positive real numbers. If abc = 6 and a + b = 2 , what is the minimum possible value of a + b + c ?**E6 / L5.** Circles A and B are drawn on a plane such that they intersect at two points. The centers of the two circles and the two intersection points lie on another circle, circle C . If the distance between the centers of circles A and B is 20 and the radius of circle A is 16 , what is the radius of circle B ?**E7.** Point P is inside rectangle ABCD . If AP = 5 , BP = 6 , and CP = 7 , what is the length of DP ?**E8 / L6.** For how many integers n is n^2 + 4 divisible by n + 2 ?**E9.** How many of the perfect squares between 1 and 10000 , inclusive, can be written as the sum of two triangular numbers? We define the n th triangular number to be 1 + 2 + 3 + ... + n , where n is a positive integer.**E10 / L7.** A small sphere of radius 1 is sitting on the ground externally tangent to a larger sphere, also sitting on the ground. If the line connecting the spheres’ centers makes a 60^o angle with the ground, what is the radius of the larger sphere?**E11 / L8.** A classroom has 12 chairs in a row and 5 distinguishable students. The teacher wants to position the students in the seats in such a way that there is at least one empty chair between any two students. In how many ways can the teacher do this?**E12 / L9.** Let there be real numbers a and b such that a/b^2 + b/a^2 = 72 and ab = 3 . Find the value of a^2 + b^2 .**E13 / L10.** Find the number of ordered pairs of positive integers (x, y) such that gcd , (x, y)+lcm , (x, y) =x + y + 8 .**E14 / L11.** Evaluate sum_{i=1}^{infty}frac{i}{4^i}=frac{1}{4} +frac{2}{16} +frac{3}{64} +... **E15 / L12.** Xavier and Olivia are playing tic-tac-toe. Xavier goes first. How many ways can the game play out such that Olivia wins on her third move? The order of the moves matters.**L1.** What is the sum of the positive divisors of 100 ?**L13.** Let ABCD be a convex quadrilateral with AC = 20 . Furthermore, let M, N, P , and Q be the midpoints of DA, AB, BC , and CD , respectively. Let X be the intersection of the diagonals of quadrilateral MNPQ . Given that NX = 12 and XP = 10 , compute the area of ABCD .**L14.** Evaluate (sqrt3 + sqrt5)^6 to the nearest integer.**L15.** In Hatland, each citizen wears either a green hat or a blue hat. Furthermore, each citizen belongs to exactly one neighborhood. On average, a green-hatted citizen has 65% of his neighbors wearing green hats, and a blue-hatted citizen has 80% of his neighbors wearing blue hats. Each neighborhood has a different number of total citizens. What is the ratio of green-hatted to blue-hatted citizens in Hatland? (A citizen is his own neighbor.)PS. You should use hide for answers. Collected [here](https://artofproblemsolving.com/community/c5h2760506p24143309).

💡Alright, so I've got this problem here about a point inside a rectangle and some distances from that point to the rectangle's corners. Let me try to visualize it first. There's a rectangle ABCD, and point P is somewhere inside it. They give me the distances from P to three of the corners: AP is 5 units, BP is 6 units, and CP is 7 units. I need to find the distance from P to the fourth corner, DP.Hmm, okay. I remember there's something called the British Flag Theorem. I think it has to do with rectangles and distances from a point to the corners. Let me recall what it says. I believe it states that for any point inside a rectangle, the sum of the squares of the distances to two opposite corners is equal to the sum of the squares of the distances to the other two opposite corners. So, if I label the rectangle's corners as A, B, C, D, then AP² + CP² should equal BP² + DP².Let me write that down to make sure I got it right:AP² + CP² = BP² + DP²Okay, so plugging in the values they gave me:AP = 5, so AP² = 25BP = 6, so BP² = 36CP = 7, so CP² = 49So substituting these into the equation:25 + 49 = 36 + DP²Let me do the math on the left side first:25 + 49 = 74So now the equation is:74 = 36 + DP²To find DP², I subtract 36 from both sides:74 - 36 = DP²38 = DP²So DP is the square root of 38. Let me check if that makes sense. Square root of 36 is 6, and square root of 49 is 7, so square root of 38 should be somewhere between 6 and 7, which seems reasonable.Wait, does this theorem apply to any rectangle, regardless of its size or the position of the point inside it? I think so. The British Flag Theorem doesn't require the rectangle to be a square or have any specific proportions. It just needs to be a rectangle, and the point can be anywhere inside it. So in this case, since ABCD is a rectangle, the theorem should hold true.Let me double-check my calculations to make sure I didn't make a mistake:AP² = 5² = 25CP² = 7² = 49BP² = 6² = 36Adding AP² and CP²: 25 + 49 = 74Subtracting BP²: 74 - 36 = 38So DP² = 38, which means DP = √38Yes, that seems correct. I don't see any errors in my steps. The British Flag Theorem provided a straightforward way to solve this problem without needing to know the exact dimensions of the rectangle or the coordinates of point P. It's a really handy theorem for these kinds of geometry problems.I wonder if there's another way to approach this problem without using the British Flag Theorem, just to confirm. Maybe by assigning coordinates to the rectangle and point P, then using the distance formula? Let's try that quickly.Let's assume rectangle ABCD has coordinates: A at (0, 0), B at (a, 0), C at (a, b), and D at (0, b). Point P has coordinates (x, y). Then:AP is the distance from A to P: √(x² + y²) = 5BP is the distance from B to P: √((x - a)² + y²) = 6CP is the distance from C to P: √((x - a)² + (y - b)²) = 7DP is the distance from D to P: √(x² + (y - b)²) = ?If I square all these equations:AP²: x² + y² = 25BP²: (x - a)² + y² = 36CP²: (x - a)² + (y - b)² = 49DP²: x² + (y - b)² = ?Now, let's subtract AP² from BP²:[(x - a)² + y²] - [x² + y²] = 36 - 25(x² - 2ax + a² + y²) - (x² + y²) = 11-2ax + a² = 11Similarly, subtract BP² from CP²:[(x - a)² + (y - b)²] - [(x - a)² + y²] = 49 - 36(y² - 2by + b²) - y² = 13-2by + b² = 13Now, let's find DP²:DP² = x² + (y - b)² = x² + y² - 2by + b²We know from AP² that x² + y² = 25, and from the previous step that -2by + b² = 13.So substituting these into DP²:DP² = 25 + 13 = 38Therefore, DP = √38Okay, so using coordinate geometry also leads me to the same answer. That gives me more confidence that √38 is indeed the correct distance from P to D.I think I've got it. The British Flag Theorem was the key here, and verifying through coordinate geometry confirmed the result. It's always good to check your work with a different method if possible, especially when dealing with geometry problems where visualizing the situation can sometimes be tricky.Another thing I might consider is whether the point P could be located in a special position within the rectangle, like near a corner or the center, but since the distances are all different, it's probably somewhere off-center. However, regardless of its position, the theorem still holds, so the specific location doesn't affect the outcome.In summary, by applying the British Flag Theorem and verifying with coordinate geometry, I've determined that the distance from point P to corner D is the square root of 38.

Consider an isosceles right triangle triangle DEF with DE = EF. A square is inscribed inside this triangle such that one vertex of the square is at the right-angle vertex of the triangle, and two of its sides are coincident with the two legs of the triangle. If the area of this square is found to be 784 text{cm}^2, determine the area (in text{cm}^2) of another square inscribed in the same triangle DEF where its sides are parallel to the hypotenuse and one of its vertices is also at the right-angle vertex.

💡Okay, so I have this problem about an isosceles right triangle, DEF, where DE equals EF. That means it's a right-angled triangle with the right angle at E, I think. They mentioned that a square is inscribed inside this triangle. The first square has one vertex at the right-angle vertex, which is E, and two of its sides are coincident with the two legs of the triangle. The area of this square is given as 784 cm². I need to find the area of another square inscribed in the same triangle, but this time, the square's sides are parallel to the hypotenuse, and one of its vertices is also at the right-angle vertex.Alright, let me break this down. First, let's visualize the triangle. Since it's an isosceles right triangle, both legs DE and EF are equal in length. Let's denote the length of each leg as 'a'. The hypotenuse DF would then be a√2, right?Now, the first square is inscribed such that one of its vertices is at E, and two of its sides lie along DE and EF. So, this square is snugly fit into the corner at E, touching both legs. The area of this square is 784 cm², so the side length of this square must be the square root of 784. Let me calculate that: √784 is 28 cm. So, each side of the first square is 28 cm.Since the square is sitting at the corner E, the legs DE and EF of the triangle are each divided into two parts: one part is the side of the square, 28 cm, and the other part is the remaining segment beyond the square. So, if the total length of each leg is 'a', then beyond the square, the remaining length on each leg would be (a - 28) cm.But wait, in an isosceles right triangle, the legs are equal, and the square inscribed in the corner will create similar triangles above it. So, the triangle above the square is also an isosceles right triangle, similar to the original triangle DEF.Let me denote the side length of the square as 's', which is 28 cm. The legs of the original triangle are each 'a', so the legs of the smaller triangle above the square would be (a - s). Since the triangles are similar, the ratio of their corresponding sides should be equal. That is, the ratio of the legs of the smaller triangle to the original triangle is (a - s)/a.But also, the hypotenuse of the smaller triangle is the same as the side of the square, right? Wait, no. The hypotenuse of the smaller triangle would actually be the side of the square, because the square is inscribed such that its sides are along the legs. Hmm, maybe I need to think about this differently.Alternatively, perhaps I can use the formula for the side length of a square inscribed in a right triangle. I recall that if a square is inscribed in a right triangle with legs 'a' and 'b', the side length 's' of the square is given by s = (a*b)/(a + b). But in this case, since it's an isosceles right triangle, a = b, so s = (a²)/(2a) = a/2. Wait, that can't be right because if a = 28√2, then s would be 14√2, but we know s is 28 cm.Hmm, maybe I'm mixing up something here. Let me try another approach.Let me denote the legs of the triangle as 'a'. The square has side length 's' = 28 cm. When the square is inscribed in the corner, it divides the triangle into two smaller triangles and a square. The two smaller triangles are similar to the original triangle.So, the legs of the original triangle are 'a', and the legs of the smaller triangle above the square would be (a - s). Since they are similar, the ratio of their corresponding sides is equal. So, the ratio of the legs is (a - s)/a, and this should be equal to the ratio of the hypotenuses.But the hypotenuse of the original triangle is a√2, and the hypotenuse of the smaller triangle is (a - s)√2. However, the hypotenuse of the smaller triangle is also equal to the side of the square, right? Because the square's side is along the hypotenuse of the smaller triangle.Wait, no. The square is sitting at the corner, so the hypotenuse of the smaller triangle is actually the same as the side of the square. So, (a - s)√2 = s. Let me write that equation:(a - s)√2 = sWe know that s = 28 cm, so plugging that in:(a - 28)√2 = 28Let me solve for 'a':(a - 28) = 28 / √2a - 28 = 14√2a = 28 + 14√2Wait, but that seems a bit complicated. Let me check my reasoning again.Alternatively, maybe the hypotenuse of the smaller triangle is not equal to the side of the square. Instead, the square's side is along the legs, so the hypotenuse of the smaller triangle is actually the same as the square's diagonal. Hmm, that might make more sense.So, the hypotenuse of the smaller triangle would be the diagonal of the square, which is s√2. Therefore, the hypotenuse of the smaller triangle is s√2, and since the smaller triangle is similar to the original triangle, the ratio of their hypotenuses is equal to the ratio of their legs.So, the hypotenuse of the original triangle is a√2, and the hypotenuse of the smaller triangle is s√2. Therefore, the ratio is (s√2)/(a√2) = s/a.But this ratio should also be equal to the ratio of the legs, which is (a - s)/a.So, s/a = (a - s)/aWait, that would imply s = a - s, which would mean a = 2s. Since s = 28, then a = 56 cm.Wait, that seems more straightforward. Let me verify that.If a = 56 cm, then the legs of the triangle are 56 cm each. The square inscribed at the corner has side length s = 28 cm, which is half of the leg length. Then, the smaller triangle above the square would have legs of (56 - 28) = 28 cm, which is half the original legs. So, the ratio is 28/56 = 1/2, which is consistent with the ratio of the hypotenuses: (28√2)/(56√2) = 1/2.Yes, that makes sense. So, the legs of the original triangle are 56 cm each.Now, moving on to the second square. This square is inscribed in the same triangle DEF, but its sides are parallel to the hypotenuse, and one of its vertices is at the right-angle vertex E.So, this square is oriented differently. Instead of having sides along the legs, it's sides are parallel to the hypotenuse DF. Therefore, the square will be placed such that one of its sides is along the hypotenuse, but since it's a square, it will have to be rotated relative to the first square.Wait, no. The problem says the sides are parallel to the hypotenuse, and one vertex is at E. So, the square is placed such that one of its vertices is at E, and its sides are parallel to DF.Let me try to visualize this. The hypotenuse DF has a slope of -1 since it's an isosceles right triangle. So, the sides of the square will also have a slope of -1. Therefore, the square will be diamond-shaped relative to the triangle.Wait, but the square has to be inscribed in the triangle, so it must touch the triangle at certain points. Since one vertex is at E, and the sides are parallel to DF, the square will extend from E towards the hypotenuse DF, but also towards the legs DE and EF.Wait, maybe it's better to draw a diagram, but since I can't do that, I'll try to imagine it.Let me denote the side length of the second square as 't'. Since the square is placed with one vertex at E and sides parallel to DF, the square will have two sides that are parallel to DF, and the other two sides will be perpendicular to DF.But since DF has a slope of -1, the sides of the square parallel to DF will also have a slope of -1, and the other sides will have a slope of 1, because they are perpendicular.Wait, no. Actually, the sides of the square parallel to DF will have the same slope as DF, which is -1. The other sides of the square, which are perpendicular to DF, will have a slope of 1, because the negative reciprocal of -1 is 1.But in this case, the square is placed such that one vertex is at E, and the sides are parallel to DF. So, the square will extend from E towards DF, but also towards the legs DE and EF.Wait, perhaps it's better to think in terms of coordinates. Let me assign coordinates to the triangle to make it easier.Let me place point E at the origin (0,0). Since it's an isosceles right triangle with legs DE and EF, let me place point D at (a, 0) and point F at (0, a), where 'a' is the length of the legs, which we found to be 56 cm.So, DE is from (0,0) to (56,0), EF is from (0,0) to (0,56), and DF is the hypotenuse from (56,0) to (0,56).Now, the first square is inscribed with sides along DE and EF, so its vertices are at (0,0), (28,0), (28,28), and (0,28). That makes sense because the side length is 28 cm.Now, the second square is inscribed with sides parallel to DF, and one vertex at E (0,0). So, the square will have sides with slope -1 and 1.Let me denote the side length of this square as 't'. The square will extend from E (0,0) along the direction of DF, but also towards the legs DE and EF.Wait, but since the square has sides parallel to DF, which has a slope of -1, the sides of the square will also have a slope of -1. So, the square will have two sides with slope -1 and two sides with slope 1.But since one vertex is at (0,0), the square will extend into the triangle. Let me try to find the coordinates of the other vertices.Let me consider the square as follows: starting at (0,0), moving along a direction with slope -1 for a distance 't√2' (since the side length is 't', and the distance along the slope is t√2). Wait, no, the side length is 't', so the distance along the direction of the side is 't'.Wait, maybe I need to parameterize the square.Alternatively, perhaps I can use similar triangles again.Since the square is inscribed with sides parallel to DF, the triangle above the square will be similar to the original triangle.Let me denote the side length of the square as 't'. The square will divide the original triangle into two smaller triangles and the square. The triangle above the square will be similar to the original triangle.Let me denote the legs of the original triangle as 'a' = 56 cm. The square has side length 't', and the triangle above it will have legs of length (a - t√2), because the square's side is at a 45-degree angle, so the reduction in each leg is t√2.Wait, that might not be correct. Let me think again.The square is placed such that its sides are parallel to DF. So, the square will touch the hypotenuse DF at some point, and also touch the legs DE and EF at some points.Let me denote the point where the square touches DF as point G, and the points where it touches DE and EF as points H and I, respectively.So, the square has vertices at E (0,0), H on DE, I on EF, and G on DF.Since the sides of the square are parallel to DF, the line EH has a slope of -1, and the line EI has a slope of 1.Wait, no. The sides of the square are parallel to DF, which has a slope of -1. So, the sides of the square that are parallel to DF will have a slope of -1. The other sides of the square will be perpendicular to DF, so they will have a slope of 1.Therefore, starting from E (0,0), the square will have two sides: one going along a line with slope -1, and the other going along a line with slope 1.Wait, but that would mean the square is actually a diamond shape relative to the coordinate system, with vertices at (0,0), (t,0), (t,t), and (0,t), but rotated 45 degrees. Hmm, no, that's not correct because the sides are parallel to DF, which is at a 45-degree angle.Wait, perhaps I need to think in terms of parametric equations.Let me consider the square as follows: starting at E (0,0), moving along a direction with slope -1 for a distance 't', which would bring us to a point (t/√2, -t/√2). But since we're in the first quadrant, the y-coordinate can't be negative. Hmm, maybe I need to adjust.Alternatively, perhaps the square extends from E (0,0) along the direction of DF, which is from (56,0) to (0,56). So, the direction vector is (-56,56), which simplifies to (-1,1). So, the direction vector is (-1,1), which has a slope of -1.Therefore, the side of the square along this direction would be from E (0,0) to a point ( -t/√2, t/√2 ), but since we can't have negative coordinates, this approach might not be correct.Wait, maybe I should consider the parametric equations of the sides of the square.Let me denote the square as having vertices at E (0,0), A, B, and C. The sides EA and EC are along the directions parallel to DF, which has a slope of -1. So, the lines EA and EC have slopes of -1 and 1, respectively.Wait, no. If the sides are parallel to DF, which has a slope of -1, then the sides of the square parallel to DF will have a slope of -1. The other sides of the square, which are perpendicular to DF, will have a slope of 1.Therefore, starting from E (0,0), one side of the square goes along a line with slope -1, and the other side goes along a line with slope 1.Let me denote the side length of the square as 't'. Then, the point A on DE will be at (t,0), and the point B on EF will be at (0,t). But wait, that's the first square, not the second one.Wait, no. The second square is placed such that its sides are parallel to DF, so the points where it touches DE and EF are not at (t,0) and (0,t), but somewhere else.Let me think differently. Let me denote the square as having vertices at E (0,0), P on DE, Q on DF, and R on EF.Since the sides EP and ER are along the directions parallel to DF, which has a slope of -1, the lines EP and ER will have slopes of -1 and 1, respectively.Wait, no. If the sides are parallel to DF, which has a slope of -1, then the sides of the square parallel to DF will have a slope of -1. The other sides, which are perpendicular to DF, will have a slope of 1.Therefore, starting from E (0,0), the square will have two sides: one going along a line with slope -1, and the other going along a line with slope 1. These two sides will meet at a point inside the triangle, forming the square.Let me denote the point where the side with slope -1 meets the hypotenuse DF as point P, and the point where the side with slope 1 meets the hypotenuse DF as point Q. Then, the square will have vertices at E (0,0), P, Q, and another point R on the other side.Wait, maybe I'm overcomplicating this. Let me try to find the coordinates of the square.Let me denote the side length of the square as 't'. The square will have two sides along the directions of DF, which is from (56,0) to (0,56). So, the direction vector is (-56,56), which simplifies to (-1,1). Therefore, the unit vector in this direction is (-1/√2, 1/√2).Since the side length of the square is 't', the displacement from E (0,0) along this direction will be t*(-1/√2, 1/√2) = (-t/√2, t/√2). But since we can't have negative coordinates, this point must lie within the triangle, so the x-coordinate must be positive. Therefore, maybe I need to adjust the direction.Alternatively, perhaps the square extends from E (0,0) towards the hypotenuse DF, but in such a way that the sides are parallel to DF. So, the square will have one vertex at E, and the opposite vertex somewhere along DF.Wait, let me consider the parametric equations of the sides of the square.Let me denote the square as follows: starting at E (0,0), moving along a line with slope -1 for a distance 't', which brings us to point P (t/√2, -t/√2). But since we can't have negative y-coordinates, this point must lie within the triangle, so the y-coordinate must be positive. Therefore, maybe the direction is different.Alternatively, perhaps the square is placed such that from E (0,0), it extends towards the hypotenuse DF along a line with slope 1, and another line with slope -1, forming the square.Wait, I'm getting confused. Maybe I should use similar triangles again.Since the square is inscribed with sides parallel to DF, the triangle above the square will be similar to the original triangle. Let me denote the side length of the square as 't'. The legs of the original triangle are 56 cm each. The legs of the smaller triangle above the square will be (56 - t√2), because the square's side is at a 45-degree angle, so the reduction in each leg is t√2.Wait, let me explain. The square has side length 't', and since it's placed at a 45-degree angle, the projection of the square onto each leg is t√2. Therefore, the remaining length on each leg beyond the square is (56 - t√2).Since the smaller triangle above the square is similar to the original triangle, the ratio of their legs is equal. So, the ratio of the legs of the smaller triangle to the original triangle is (56 - t√2)/56.But this ratio should also be equal to the ratio of their hypotenuses. The hypotenuse of the original triangle is 56√2, and the hypotenuse of the smaller triangle is (56 - t√2)√2.But the hypotenuse of the smaller triangle is also equal to the side of the square, right? Because the square is inscribed such that its side is along the hypotenuse of the smaller triangle.Wait, no. The hypotenuse of the smaller triangle is actually the same as the side of the square, because the square is placed such that its side is along the hypotenuse of the smaller triangle.Wait, that might make sense. So, the hypotenuse of the smaller triangle is equal to the side length of the square, 't'. Therefore:(56 - t√2)√2 = tLet me solve this equation for 't':(56 - t√2)√2 = t56√2 - t√2 * √2 = t56√2 - t*2 = t56√2 = t + 2t56√2 = 3tt = (56√2)/3Wait, that seems a bit messy. Let me check my reasoning again.Alternatively, perhaps the hypotenuse of the smaller triangle is not equal to 't', but rather, the side of the square is 't', and the hypotenuse of the smaller triangle is t√2.Wait, that might make more sense. Because the square has side 't', so its diagonal is t√2, which would be the hypotenuse of the smaller triangle.So, the hypotenuse of the smaller triangle is t√2, and the hypotenuse of the original triangle is 56√2. Therefore, the ratio of the hypotenuses is (t√2)/(56√2) = t/56.Since the triangles are similar, this ratio should also be equal to the ratio of their legs. The legs of the smaller triangle are (56 - t√2), so the ratio is (56 - t√2)/56.Therefore:t/56 = (56 - t√2)/56Multiplying both sides by 56:t = 56 - t√2Now, solving for 't':t + t√2 = 56t(1 + √2) = 56t = 56 / (1 + √2)To rationalize the denominator:t = 56 / (1 + √2) * (1 - √2)/(1 - √2)t = 56(1 - √2) / (1 - 2)t = 56(1 - √2) / (-1)t = 56(√2 - 1)So, t = 56(√2 - 1) cm.Now, the area of the second square is t²:Area = [56(√2 - 1)]²= 56² * (√2 - 1)²= 3136 * ( (√2)² - 2√2 + 1 )= 3136 * (2 - 2√2 + 1)= 3136 * (3 - 2√2)Hmm, that seems complicated. Let me calculate it numerically to see if it makes sense.First, calculate (√2 - 1):√2 ≈ 1.4142√2 - 1 ≈ 0.4142So, t ≈ 56 * 0.4142 ≈ 23.195 cmThen, t² ≈ (23.195)² ≈ 538.04 cm²Wait, but the first square had an area of 784 cm², which is larger than this. That doesn't make sense because the second square should be smaller, but not necessarily by that much.Wait, maybe I made a mistake in my reasoning. Let me go back.I said that the hypotenuse of the smaller triangle is t√2, but actually, the hypotenuse of the smaller triangle is the same as the side of the square, which is 't', because the square is placed such that its side is along the hypotenuse of the smaller triangle.Wait, no. The square is placed such that its sides are parallel to the hypotenuse, so the hypotenuse of the smaller triangle is actually the same as the side of the square, 't'.Wait, that would mean:The hypotenuse of the smaller triangle is 't', so:(56 - t√2)√2 = tLet me solve this:(56 - t√2)√2 = t56√2 - t*2 = t56√2 = 3tt = (56√2)/3 ≈ (56*1.4142)/3 ≈ (79.195)/3 ≈ 26.398 cmThen, t² ≈ (26.398)² ≈ 702.8 cm²But this is still less than 784 cm², which is the area of the first square. That seems contradictory because the first square is placed at the corner, and the second square is placed inside the triangle, but perhaps it's possible.Wait, but let me check the calculations again.If the hypotenuse of the smaller triangle is 't', then:(56 - t√2)√2 = t56√2 - 2t = t56√2 = 3tt = (56√2)/3Yes, that's correct.So, t ≈ (56*1.4142)/3 ≈ 79.195/3 ≈ 26.398 cmThen, the area is t² ≈ 702.8 cm²But the first square had an area of 784 cm², which is larger. That seems odd because the second square is placed inside the triangle, but perhaps it's smaller.Wait, but actually, the first square is placed at the corner, so it's larger, and the second square is placed towards the hypotenuse, so it's smaller. So, it's possible that the second square has a smaller area.But let me verify the reasoning again.The square is placed such that its sides are parallel to the hypotenuse DF, and one vertex is at E (0,0). The square will touch the hypotenuse DF at some point, and also touch the legs DE and EF at some points.Let me denote the side length of the square as 't'. The square will form a smaller triangle above it, similar to the original triangle.The legs of the original triangle are 56 cm each. The legs of the smaller triangle will be (56 - t√2), because the square's side is at a 45-degree angle, so the reduction in each leg is t√2.The hypotenuse of the smaller triangle is (56 - t√2)√2, which should be equal to the side length of the square, 't'.So:(56 - t√2)√2 = t56√2 - 2t = t56√2 = 3tt = (56√2)/3Yes, that's correct.So, t = (56√2)/3 cmThen, the area of the square is t² = [(56√2)/3]^2 = (56² * 2)/9 = (3136 * 2)/9 = 6272/9 ≈ 696.89 cm²Wait, that's approximately 696.89 cm², which is less than 784 cm², which makes sense.But let me calculate it exactly:6272 ÷ 9 = 696.888... cm²So, the area is 6272/9 cm², which is approximately 696.89 cm².But the problem asks for the area in cm², so I can write it as 6272/9 cm², but perhaps it can be simplified.Wait, 6272 ÷ 9: Let me see if 6272 is divisible by 9.6 + 2 + 7 + 2 = 17, which is not divisible by 9, so 6272/9 is the simplest form.Alternatively, I can write it as (56√2/3)² = (56² * 2)/9 = 3136*2/9 = 6272/9.So, the area of the second square is 6272/9 cm².But let me check if there's another way to approach this problem.Alternatively, perhaps I can use coordinate geometry.Let me place the triangle with E at (0,0), D at (56,0), and F at (0,56). The hypotenuse DF is the line x + y = 56.The square is placed with one vertex at E (0,0), and sides parallel to DF. Let me denote the side length of the square as 't'.The square will have two sides along the lines y = -x + c and y = -x + d, where c and d are constants. But since the square is placed at E (0,0), one of these lines will pass through E.Wait, no. The sides of the square parallel to DF (which has a slope of -1) will have equations y = -x + t and y = -x, but since E is at (0,0), the line y = -x passes through E, but that would imply the square is extending into negative coordinates, which isn't possible.Wait, perhaps I need to adjust the equations.Let me consider the square as follows: starting at E (0,0), the square extends towards the hypotenuse DF along a line with slope -1. The other side of the square extends towards the other leg along a line with slope 1.Wait, but the square has to be a square, so the distance from E along both directions must be equal.Let me denote the side length as 't'. Then, the point where the square meets DE is at (t,0), and the point where it meets EF is at (0,t). But that's the first square, not the second one.Wait, no. The second square is placed such that its sides are parallel to DF, so the points where it meets DE and EF are not at (t,0) and (0,t), but somewhere else.Let me denote the point where the square meets DE as (a,0) and the point where it meets EF as (0,b). Since the sides of the square are parallel to DF, the line connecting (a,0) and (0,b) must have a slope of -1.So, the slope between (a,0) and (0,b) is (b - 0)/(0 - a) = -b/a. Since this slope must be -1, we have:-b/a = -1b/a = 1b = aSo, a = b.Therefore, the square meets DE at (a,0) and EF at (0,a). The side length of the square is the distance between (a,0) and (0,a), which is √(a² + a²) = a√2. But since the side length of the square is 't', we have:t = a√2a = t/√2Now, the square also touches the hypotenuse DF at some point. The hypotenuse DF is the line x + y = 56.The square has vertices at E (0,0), (a,0), (0,a), and the fourth vertex somewhere on DF.Wait, no. Actually, the square will have four vertices: E (0,0), (a,0), (0,a), and another point which is the intersection of the lines y = -x + c and x + y = 56.Wait, let me clarify.The square has sides parallel to DF, so the sides are along the lines y = -x + c and y = -x + d, where c and d are constants.Since one vertex is at E (0,0), which lies on the line y = -x, but that's not one of the sides of the square. Wait, perhaps I need to think differently.Alternatively, the square has two sides along the directions of DF, which is slope -1, and two sides along the directions perpendicular to DF, which is slope 1.So, starting from E (0,0), moving along a direction with slope -1 for a distance 't', which brings us to a point (t/√2, -t/√2). But since we can't have negative coordinates, this point must lie within the triangle, so the y-coordinate must be positive. Therefore, maybe the direction is different.Wait, perhaps the square extends from E (0,0) towards the hypotenuse DF along a line with slope 1, and another line with slope -1, forming the square.Wait, no. The sides of the square are parallel to DF, which has a slope of -1, so the sides of the square must have a slope of -1.Therefore, starting from E (0,0), the square will have two sides: one going along a line with slope -1, and the other going along a line with slope 1 (perpendicular to DF).Wait, but the square must have all sides equal and at right angles. So, if two sides are along slope -1 and 1, then the other two sides must also be along these slopes.Wait, perhaps the square is actually a diamond shape, with vertices at E (0,0), (t,0), (t,t), and (0,t), but rotated 45 degrees. But that's the first square, not the second one.Wait, I'm getting stuck here. Maybe I should use the similar triangles approach again.We have the original triangle with legs 56 cm each. The square is inscribed with sides parallel to DF, so the triangle above the square is similar to the original triangle.Let me denote the side length of the square as 't'. The legs of the smaller triangle above the square are (56 - t√2), as before.The hypotenuse of the smaller triangle is (56 - t√2)√2, which should be equal to the side length of the square, 't'.So:(56 - t√2)√2 = t56√2 - 2t = t56√2 = 3tt = (56√2)/3Yes, that's correct.Therefore, the area of the square is t² = [(56√2)/3]^2 = (56² * 2)/9 = (3136 * 2)/9 = 6272/9 cm².Simplifying 6272/9:6272 ÷ 9 = 696.888... cm²So, the area is 6272/9 cm², which is approximately 696.89 cm².But let me check if this makes sense. The first square had an area of 784 cm², which is larger, so the second square being smaller makes sense.Alternatively, perhaps I can express 6272/9 as a mixed number, but since the problem asks for the area in cm², and it's likely to be a fraction, I can leave it as 6272/9 cm².Wait, but 6272 divided by 9: 9*696 = 6264, so 6272 - 6264 = 8, so it's 696 and 8/9 cm².So, 696 8/9 cm².But the problem might expect an exact value, so 6272/9 cm² is acceptable.Alternatively, perhaps I made a mistake in the similar triangles approach. Let me try another method.Let me consider the coordinates again. The square has vertices at E (0,0), P on DE, Q on EF, and R on DF.Since the sides EP and ER are along the directions parallel to DF, which has a slope of -1, the lines EP and ER have slopes of -1 and 1, respectively.Wait, no. If the sides are parallel to DF, which has a slope of -1, then the sides of the square must have a slope of -1. Therefore, the lines EP and ER have slopes of -1 and 1, respectively.Wait, no. If the sides are parallel to DF, which has a slope of -1, then the sides of the square must have a slope of -1. Therefore, the lines EP and ER have slopes of -1 and 1, respectively.Wait, but that would mean that the square is actually a diamond shape, with sides along the lines y = -x and y = x, but that's not possible because the square must be inside the triangle.Wait, perhaps I need to consider the parametric equations of the sides.Let me denote the square as follows: starting at E (0,0), moving along a direction with slope -1 for a distance 't', which brings us to point P (t/√2, -t/√2). But since we can't have negative coordinates, this point must lie within the triangle, so the y-coordinate must be positive. Therefore, maybe the direction is different.Alternatively, perhaps the square extends from E (0,0) towards the hypotenuse DF along a line with slope 1, and another line with slope -1, forming the square.Wait, I'm getting stuck again. Maybe I should accept that the area is 6272/9 cm² and proceed.But let me check the calculation one more time.We have:t = (56√2)/3t² = (56² * 2)/9 = (3136 * 2)/9 = 6272/9Yes, that's correct.So, the area of the second square is 6272/9 cm², which is approximately 696.89 cm².But wait, the problem states that the first square has an area of 784 cm², which is 28². The second square has an area of 6272/9 cm², which is approximately 696.89 cm². That seems plausible.Alternatively, perhaps I can express 6272/9 as follows:6272 ÷ 9 = 696.888... = 696 + 8/9So, 696 8/9 cm².But the problem might expect an exact value, so 6272/9 cm² is the precise answer.Alternatively, perhaps I can simplify 6272/9:Divide numerator and denominator by GCD(6272,9). The GCD of 6272 and 9 is 1, so it cannot be simplified further.Therefore, the area of the second square is 6272/9 cm².But let me check if there's another approach to confirm this result.Another approach: Let's consider the coordinates of the square.The square has one vertex at E (0,0), and sides parallel to DF (slope -1). Let me denote the side length as 't'. The square will have two other vertices on DE and EF, and the fourth vertex on DF.Let me denote the point on DE as (a,0) and the point on EF as (0,b). Since the sides of the square are parallel to DF, the line connecting (a,0) and (0,b) must have a slope of -1.So, the slope between (a,0) and (0,b) is (b - 0)/(0 - a) = -b/a = -1Therefore, -b/a = -1 => b/a = 1 => b = aSo, a = b.Now, the distance between (a,0) and (0,a) is the side length of the square, which is t.The distance between (a,0) and (0,a) is √(a² + a²) = a√2 = tTherefore, a = t/√2Now, the fourth vertex of the square is on DF, which is the line x + y = 56.The fourth vertex is the intersection of the lines y = -x + c and x + y = 56.But since the square has sides parallel to DF, the line from (a,0) to the fourth vertex must have a slope of -1.Wait, no. The sides of the square are parallel to DF, so the sides have a slope of -1. Therefore, the line from (a,0) to the fourth vertex must have a slope of -1.Let me denote the fourth vertex as (x,y). Since it's on DF, x + y = 56.The line from (a,0) to (x,y) has a slope of (y - 0)/(x - a) = -1So:(y)/(x - a) = -1y = - (x - a)y = -x + aBut since (x,y) is on DF, x + y = 56, so:x + (-x + a) = 56x - x + a = 56a = 56Wait, that can't be right because a = t/√2, and t is less than 56.Wait, that suggests a = 56, which would mean t = 56√2, but that's larger than the leg length of 56 cm, which is impossible.Therefore, I must have made a mistake in my reasoning.Wait, let's go back.We have the square with vertices at E (0,0), (a,0), (0,a), and (x,y) on DF.The line from (a,0) to (x,y) has a slope of -1, so:(y - 0)/(x - a) = -1y = - (x - a)y = -x + aBut (x,y) is on DF, so x + y = 56.Substituting y = -x + a into x + y = 56:x + (-x + a) = 560 + a = 56a = 56But a = t/√2, so t = 56√2 cm.But the leg length is 56 cm, so t = 56√2 cm would make the square larger than the triangle, which is impossible.Therefore, this approach must be incorrect.Wait, perhaps the line from (a,0) to (x,y) is not a side of the square, but rather, the side of the square is from (a,0) to (x,y), which has a slope of -1 and length 't'.So, the distance between (a,0) and (x,y) is 't', and the slope is -1.So:y - 0 = -1*(x - a)y = -x + aAnd the distance between (a,0) and (x,y) is t:√[(x - a)² + (y - 0)²] = t√[(x - a)² + (-x + a)²] = t√[(x - a)² + (x - a)²] = t√[2(x - a)²] = t√2 * |x - a| = t|x - a| = t/√2Since x < a (because the square is inside the triangle), x - a = -t/√2x = a - t/√2Now, since (x,y) is on DF, x + y = 56.From y = -x + a, we have:x + (-x + a) = 56a = 56Again, this leads to a = 56, which is impossible because a = t/√2, and t must be less than 56.Therefore, this approach is flawed.Perhaps I need to consider that the square has two sides along the directions of DF, but not necessarily connecting to the legs DE and EF.Wait, maybe the square is placed such that it only touches the hypotenuse DF and the two legs DE and EF at one point each, not along the entire side.In that case, the square would have one vertex at E (0,0), and the other three vertices touching DE, EF, and DF.Let me denote the side length of the square as 't'. The square will have vertices at E (0,0), P on DE, Q on EF, and R on DF.The sides EP and ER are along the directions parallel to DF, which has a slope of -1.Therefore, the coordinates of P and Q can be expressed as follows:Point P is on DE, so its coordinates are (p,0). The line from E (0,0) to P (p,0) is along the x-axis, but since the side is parallel to DF, which has a slope of -1, this approach might not work.Wait, no. The side from E to P must have a slope of -1, so P cannot be on DE unless P is at (0,0), which is E itself. Therefore, this approach is incorrect.I think I'm stuck here. Maybe I should accept that the area is 6272/9 cm² based on the similar triangles approach, even though I'm having trouble visualizing it.Alternatively, perhaps the area of the second square is the same as the first square, but that seems unlikely because their orientations are different.Wait, in the initial problem, the user provided a solution where the area of the second square was also 784 cm², but that seems incorrect because the second square is placed differently.Wait, let me check the initial problem again.The user wrote:"Given the area of the first square is 784 cm², the side length of this square, say s, can be calculated as follows:s² = 784 ⇒ s = 28 cmSince this square is positioned such that its sides coincide with the legs of triangle DEF, we understand that DE = EF = √2 · s. Thus, we can calculate the legs of the triangle:DE = EF = √2 · 28 = 28√2 cmNow move to the second configuration of the square which is parallel to the hypotenuse and touching at the right-angle vertex D. In this case, if the side length of this new square is t, then t can be expressed in terms of the triangle's leg:t = leg / √2 = 28√2 / √2 = 28 cmHence, the area of this second square is:t² = 28² = 784 cm²boxed{784 text{cm}^2}"Wait, but in this solution, the user assumes that the side length of the second square is leg / √2, which is 28√2 / √2 = 28 cm, leading to the same area as the first square. But this seems incorrect because the second square is placed differently.I think the mistake in the initial solution is assuming that the side length of the second square is leg / √2, which is not necessarily correct.In reality, the side length of the second square is smaller than the first square, as we calculated earlier as 6272/9 cm² ≈ 696.89 cm².Therefore, the correct area of the second square is 6272/9 cm².But to confirm, let me consider the following:The first square has side length 28 cm, area 784 cm².The second square has side length t = (56√2)/3 cm, area t² = 6272/9 cm² ≈ 696.89 cm².Therefore, the area of the second square is 6272/9 cm².But let me check if this can be simplified or expressed differently.6272 ÷ 9 = 696.888... cm²Alternatively, 6272/9 can be written as (56² * 2)/9 = (3136 * 2)/9 = 6272/9.Yes, that's correct.Therefore, the area of the second square is 6272/9 cm².But to express this as a mixed number, it's 696 8/9 cm².But since the problem asks for the area in cm², and it's likely to be a fraction, I can write it as 6272/9 cm².However, perhaps I can simplify this fraction.Divide numerator and denominator by GCD(6272,9). The GCD is 1, so it cannot be simplified further.Therefore, the area is 6272/9 cm².But let me check if this is the correct approach.Yes, using similar triangles, we found that t = (56√2)/3, so t² = 6272/9 cm².Therefore, the area of the second square is 6272/9 cm².

A group of 30 friends were discussing a large positive integer. Each friend, starting with the first, said the integer can be divided by an incremental number: "It can be divided by 1," said the first friend; "It can be divided by 2," said the second friend, and so on up to 30. However, exactly three friends made incorrect statements with their numbers being consecutive. Identify the least possible integer they were discussing if friends' incorrect statements were 27, 28, and 29.

💡Okay, so I'm trying to solve this problem where 30 friends are discussing a large positive integer. Each friend, starting from the first, says that the integer can be divided by an incremental number: the first friend says it's divisible by 1, the second by 2, and so on up to 30. However, exactly three friends made incorrect statements, and their numbers are consecutive. The incorrect numbers are 27, 28, and 29. I need to find the least possible integer they were discussing.Alright, let me break this down. The integer N must be divisible by all numbers from 1 to 30 except for 27, 28, and 29. So, N should be the least common multiple (LCM) of all the numbers from 1 to 30, excluding 27, 28, and 29. That makes sense because the LCM of a set of numbers is the smallest number that is divisible by each of them.First, I need to recall how to compute the LCM of multiple numbers. The LCM of a set of numbers is found by taking the highest power of all prime numbers that appear in the factorization of those numbers. So, for example, the LCM of 4 and 6 is 12 because 4 is 2² and 6 is 2×3, so the highest powers are 2² and 3¹, giving 12.Given that, I need to list all the numbers from 1 to 30, exclude 27, 28, and 29, and then find their LCM. Let me list the numbers:1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 30.Now, I need to factor each of these numbers into their prime factors to determine the highest powers of each prime number.Let's start:1: 1 (doesn't affect LCM)2: 23: 34: 2²5: 56: 2×37: 78: 2³9: 3²10: 2×511: 1112: 2²×313: 1314: 2×715: 3×516: 2⁴17: 1718: 2×3²19: 1920: 2²×521: 3×722: 2×1123: 2324: 2³×325: 5²26: 2×1330: 2×3×5Now, let's list out all the prime numbers involved: 2, 3, 5, 7, 11, 13, 17, 19, 23.Next, for each prime number, find the highest power that appears in the factorizations above.Starting with 2:- The highest power of 2 is in 16, which is 2⁴.For 3:- The highest power of 3 is in 9 and 18, which is 3².For 5:- The highest power of 5 is in 25, which is 5².For 7:- The highest power is 7¹.For 11:- The highest power is 11¹.For 13:- The highest power is 13¹.For 17:- The highest power is 17¹.For 19:- The highest power is 19¹.For 23:- The highest power is 23¹.So, the LCM would be the product of these highest powers:LCM = 2⁴ × 3² × 5² × 7 × 11 × 13 × 17 × 19 × 23.Now, I need to compute this value step by step.First, compute 2⁴:2⁴ = 16.Next, 3²:3² = 9.5²:5² = 25.So, multiplying these together: 16 × 9 = 144; 144 × 25 = 3600.Now, multiply by 7:3600 × 7 = 25200.Next, multiply by 11:25200 × 11 = 277200.Then, multiply by 13:277200 × 13. Let's compute that:277200 × 10 = 2,772,000277200 × 3 = 831,600Adding them together: 2,772,000 + 831,600 = 3,603,600.Next, multiply by 17:3,603,600 × 17. Let's break this down:3,603,600 × 10 = 36,036,0003,603,600 × 7 = 25,225,200Adding them together: 36,036,000 + 25,225,200 = 61,261,200.Now, multiply by 19:61,261,200 × 19. Let's compute:61,261,200 × 10 = 612,612,00061,261,200 × 9 = 551,350,800Adding them together: 612,612,000 + 551,350,800 = 1,163,962,800.Finally, multiply by 23:1,163,962,800 × 23. Let's compute this step by step:1,163,962,800 × 20 = 23,279,256,0001,163,962,800 × 3 = 3,491,888,400Adding them together: 23,279,256,000 + 3,491,888,400 = 26,771,144,400.Wait, that seems too large. Let me check my calculations again because the final answer provided earlier was 1,225,224,000, which is much smaller.Hmm, maybe I made a mistake in the multiplication steps. Let me go back and verify each step carefully.Starting from the beginning:LCM = 2⁴ × 3² × 5² × 7 × 11 × 13 × 17 × 19 × 23.Compute step by step:2⁴ = 163² = 95² = 25Multiply these together: 16 × 9 = 144; 144 × 25 = 3600.Now, 3600 × 7 = 25,200.25,200 × 11 = 277,200.277,200 × 13:Let me compute 277,200 × 10 = 2,772,000277,200 × 3 = 831,600Adding: 2,772,000 + 831,600 = 3,603,600.3,603,600 × 17:3,603,600 × 10 = 36,036,0003,603,600 × 7 = 25,225,200Adding: 36,036,000 + 25,225,200 = 61,261,200.61,261,200 × 19:61,261,200 × 10 = 612,612,00061,261,200 × 9 = 551,350,800Adding: 612,612,000 + 551,350,800 = 1,163,962,800.1,163,962,800 × 23:Let me compute 1,163,962,800 × 20 = 23,279,256,0001,163,962,800 × 3 = 3,491,888,400Adding: 23,279,256,000 + 3,491,888,400 = 26,771,144,400.Wait, that's the same result as before. But the initial answer was 1,225,224,000, which is much smaller. Did I include all the numbers correctly?Wait, maybe I made a mistake in the initial prime factorization. Let me double-check the highest powers.Looking back at the numbers from 1 to 30, excluding 27, 28, 29:16 is 2⁴, which is correct.9 is 3², correct.25 is 5², correct.7 is 7¹, correct.11, 13, 17, 19, 23 are all primes to the first power.So, the LCM should indeed be 2⁴ × 3² × 5² × 7 × 11 × 13 × 17 × 19 × 23.But when I compute that, I get 26,771,144,400, which is way larger than the initial answer. Hmm.Wait, perhaps the initial answer was incorrect. Let me check the calculation again.Alternatively, maybe I missed that 28 is 4×7, and since 4 is already included in 2⁴, and 7 is included, but since 28 is excluded, does that affect the LCM? Wait, no, because we're excluding 28, so we don't need to include it in the LCM. So, the LCM is still based on the numbers from 1 to 30 excluding 27, 28, 29.Wait, but 28 is 4×7, and since 4 is already in 2⁴, and 7 is already included, excluding 28 doesn't change the LCM because 28's factors are already covered by 2⁴ and 7.Similarly, 27 is 3³, but since we're excluding 27, we don't need to include 3³ in the LCM. The highest power of 3 in the remaining numbers is 3² from 9 and 18.Similarly, 29 is a prime number, so excluding it means we don't include 29 in the LCM.So, the LCM should indeed be 2⁴ × 3² × 5² × 7 × 11 × 13 × 17 × 19 × 23.But when I compute that, I get 26,771,144,400, which is much larger than the initial answer of 1,225,224,000.Wait, maybe I made a mistake in the multiplication steps. Let me try a different approach.Let me compute the LCM in smaller steps.First, compute the LCM of numbers 1-10, then build up.But that might take too long. Alternatively, let me see if I can find a mistake in the multiplication.Wait, perhaps I made a mistake in the initial multiplication after 1,163,962,800 × 23.Let me compute 1,163,962,800 × 23.First, 1,163,962,800 × 20 = 23,279,256,000.Then, 1,163,962,800 × 3 = 3,491,888,400.Adding these together: 23,279,256,000 + 3,491,888,400.Let me add them step by step:23,279,256,000+3,491,888,400= (23,279,256,000 + 3,000,000,000) + 491,888,400= 26,279,256,000 + 491,888,400= 26,771,144,400.Yes, that's correct. So, the LCM is indeed 26,771,144,400.But the initial answer was 1,225,224,000, which is much smaller. So, there must be a mistake in the initial approach.Wait, perhaps the initial answer was incorrect because it didn't account for all the necessary factors. Let me check the initial answer's prime factors.The initial answer was 1,225,224,000.Let me factorize this number:1,225,224,000.Divide by 1000: 1,225,224.Now, factorize 1,225,224.Divide by 2: 612,612Divide by 2: 306,306Divide by 2: 153,153Divide by 3: 51,051Divide by 3: 17,017Divide by 7: 2,431Divide by 11: 221Divide by 13: 17So, the prime factors are 2³ × 3² × 5³ × 7 × 11 × 13 × 17.Wait, but in our LCM, we have 2⁴, 3², 5², 7, 11, 13, 17, 19, 23.So, the initial answer is missing 19 and 23, and has higher powers of 2 and 5.Therefore, the initial answer is incorrect because it doesn't include the primes 19 and 23, which are necessary since they are in the list of numbers from 1 to 30 (19 and 23 are included, so their primes must be in the LCM).Therefore, the correct LCM should indeed include 19 and 23, making it much larger.Wait, but in the initial problem, the friends are discussing a number that is not divisible by 27, 28, and 29. So, N must not be divisible by these three numbers.But N must be divisible by all other numbers from 1 to 30. So, the LCM should include all the necessary prime factors from the other numbers.Wait, but 27 is 3³, and since N is not divisible by 27, it means that the highest power of 3 in N must be less than 3³, i.e., at most 3².Similarly, 28 is 4×7, which is 2²×7. Since N is not divisible by 28, but N must be divisible by 4 and 7 because 4 and 7 are in the list. Wait, no, because 28 is excluded, but 4 and 7 are still included. So, N must be divisible by 4 and 7, but not by 28. However, if N is divisible by both 4 and 7, it would automatically be divisible by 28, which contradicts the condition. Therefore, there's a mistake here.Wait, that's a crucial point. If N is divisible by both 4 and 7, then N must be divisible by their LCM, which is 28. But the problem states that N is not divisible by 28. Therefore, N cannot be divisible by both 4 and 7. But 4 and 7 are in the list of numbers that N must be divisible by, except for 27, 28, 29. Wait, no, the problem says that exactly three friends made incorrect statements, which are 27, 28, 29. So, N is not divisible by 27, 28, 29, but must be divisible by all others from 1 to 30.But if N must be divisible by 4 and 7, then it must be divisible by 28, which contradicts the condition that N is not divisible by 28. Therefore, there's an inconsistency here.Wait, that means that the initial assumption is incorrect. If N must be divisible by all numbers from 1 to 30 except 27, 28, 29, then N must be divisible by 4 and 7, which would imply it's divisible by 28, which is excluded. Therefore, it's impossible for N to be divisible by 4 and 7 and not be divisible by 28. Therefore, the problem as stated has no solution because the conditions are contradictory.But the problem says that exactly three friends made incorrect statements, which are 27, 28, 29. So, N is not divisible by these three, but must be divisible by all others. However, as we've just seen, if N is divisible by 4 and 7, it must be divisible by 28, which is excluded. Therefore, the only way for N to not be divisible by 28 is if it's not divisible by 4 or 7. But 4 and 7 are in the list of numbers that N must be divisible by, so that's a contradiction.Therefore, the problem as stated has no solution because it's impossible for N to be divisible by all numbers from 1 to 30 except 27, 28, 29, because 28 is the LCM of 4 and 7, which are required to be divisors of N.Wait, but maybe I'm misunderstanding the problem. Perhaps the three incorrect statements are consecutive numbers, but not necessarily that N is not divisible by those three numbers. Wait, no, the problem says that exactly three friends made incorrect statements with their numbers being consecutive. So, the numbers 27, 28, 29 are the ones for which N is not divisible by them. Therefore, N must be divisible by all other numbers from 1 to 30.But as we've seen, if N is divisible by 4 and 7, it must be divisible by 28, which is excluded. Therefore, the problem is impossible as stated because it's impossible for N to satisfy all the conditions.But the initial answer provided was 1,225,224,000, which suggests that perhaps the problem was intended to have a solution, so maybe I made a mistake in my reasoning.Wait, perhaps the three incorrect statements are not necessarily consecutive in the sense of being 27, 28, 29, but just three consecutive numbers somewhere in the range. But the problem specifically states that the incorrect statements were 27, 28, and 29, so they are consecutive.Alternatively, maybe the problem allows for N to not be divisible by 28, even though it's divisible by 4 and 7, but that's mathematically impossible because LCM(4,7)=28.Therefore, the problem as stated has no solution because it's impossible for N to be divisible by 4 and 7 and not be divisible by 28. Therefore, the initial answer must be incorrect because it doesn't account for this contradiction.Alternatively, perhaps the problem allows for N to not be divisible by 28, but then N must not be divisible by either 4 or 7, which contradicts the requirement that N must be divisible by all numbers except 27, 28, 29.Therefore, the problem is impossible as stated, and there is no such integer N that satisfies all the given conditions.But since the initial answer was provided, perhaps I made a mistake in my reasoning. Let me try again.Wait, perhaps the problem allows for N to not be divisible by 28, but still be divisible by 4 and 7. But mathematically, if N is divisible by both 4 and 7, it must be divisible by their LCM, which is 28. Therefore, N cannot be divisible by 4 and 7 and not be divisible by 28. Therefore, the problem is impossible because it requires N to be divisible by 4 and 7, but not by 28, which is impossible.Therefore, the problem as stated has no solution, and the initial answer of 1,225,224,000 is incorrect because it doesn't account for this contradiction.Alternatively, perhaps the problem intended that the three incorrect statements are not necessarily consecutive in the sense of being 27, 28, 29, but just three consecutive numbers somewhere else, but the problem specifically states that the incorrect statements were 27, 28, and 29.Therefore, the conclusion is that the problem has no solution because it's impossible for N to satisfy all the given conditions.

a train 280 m long , running with a speed of 63 km / hr will pass a tree in

💡First, I need to convert the train's speed from kilometers per hour to meters per second to match the units of the train's length.Next, I'll use the formula for time, which is distance divided by speed, to calculate how long it takes for the entire train to pass the tree.Finally, I'll perform the calculation and present the result in a clear and concise manner.

What is the smallest number which, when increased by some number, is divisible by 8, 11, and 24? The answer is 255.

💡To find the smallest number which, when increased by some number, is divisible by 8, 11, and 24, we need to determine the least common multiple (LCM) of these three numbers. The LCM is the smallest number that is a multiple of each of the given numbers.First, we perform the prime factorization of each number:- 8 can be factored into (2^3).- 11 is a prime number, so its prime factorization is simply 11.- 24 can be factored into (2^3 times 3).Next, we identify the highest powers of all prime factors present in the factorizations:- The highest power of 2 is (2^3) (from both 8 and 24).- The highest power of 11 is 11 (since it only appears in 11).- The highest power of 3 is 3 (from 24).The LCM is then calculated by multiplying these highest powers together:[text{LCM} = 2^3 times 11 times 3 = 8 times 11 times 3 = 88 times 3 = 264]We are looking for the smallest number such that when it is increased by some number, the result is 264. Let this smallest number be (N), and the number to be added be (x). Therefore:[N + x = 264]Given that the answer is 255, we substitute (N = 255) into the equation:[255 + x = 264]Solving for (x):[x = 264 - 255 = 9]Thus, the smallest number is 255, and when increased by 9, it becomes 264, which is divisible by 8, 11, and 24.

Released under the MIT License.

has loaded