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question:The weights of two friends Ram and Shyam are in the ratio 2 : 5. Ram's weight is increased by 10%, and the total weight of Ram and Shyam becomes 82.8 kg, with an increase of 15%. By what percent did the weight of Shyam have to be increased?

answer:Let's denote Ram's original weight as ( R ) and Shyam's original weight as ( S ). According to the problem, the ratio of their weights is ( 2 : 5 ), so we can write: [ R : S = 2 : 5 ] This means that ( R = 2k ) and ( S = 5k ) for some constant ( k ). Now, Ram's weight is increased by 10%, so his new weight is ( R + 0.10R = 1.10R ). The total original weight of Ram and Shyam is ( R + S = 2k + 5k = 7k ). The total new weight of Ram and Shyam is 82.8 kg, which is a 15% increase from their original total weight. So, we can write: [ 1.15(7k) = 82.8 ] Now, let's solve for ( k ): [ 8.05k = 82.8 ] [ k = frac{82.8}{8.05} ] [ k = 10.28 ] Now we can find Ram's original weight ( R ) and Shyam's original weight ( S ): [ R = 2k = 2 times 10.28 = 20.56 text{ kg} ] [ S = 5k = 5 times 10.28 = 51.4 text{ kg} ] Since the total new weight is 82.8 kg and Ram's new weight is ( 1.10R ), we can find Shyam's new weight ( S' ): [ S' = 82.8 - 1.10R ] [ S' = 82.8 - 1.10 times 20.56 ] [ S' = 82.8 - 22.616 ] [ S' = 60.184 text{ kg} ] Now we can calculate the percentage increase in Shyam's weight: [ text{Percentage increase} = frac{text{New weight} - text{Original weight}}{text{Original weight}} times 100 ] [ text{Percentage increase} = frac{60.184 - 51.4}{51.4} times 100 ] [ text{Percentage increase} = frac{8.784}{51.4} times 100 ] [ text{Percentage increase} approx 17.09% ] So, Shyam's weight had to be increased by approximately boxed{17.09%} .

question:Madeline has 80 fair coins. She flips all the coins. Any coin that lands on tails is tossed again. Additionally, any coin that lands on heads in the first two tosses is also tossed again, but only once. What is the expected number of coins that are heads after these conditions? textbf{(A)} 30 qquad textbf{(B)} 40 qquad textbf{(C)} 50 qquad textbf{(D)} 60

answer:To solve for the expected number of coins showing heads, we'll use the probability and expected values again, considering the new conditions: 1. **Probability Analysis for each Coin:** - Probability a coin lands heads on the first toss (and is tossed again): frac{1}{2}. Probability it shows heads again on this second toss is frac{1}{2} times frac{1}{2} = frac{1}{4}. - Probability a coin lands tails on the first toss and is tossed again: frac{1}{2}. Probability it then shows heads on the second toss and is tossed again: frac{1}{2} times frac{1}{2} = frac{1}{4}. Probability it shows heads on this third toss is frac{1}{4} times frac{1}{2} = frac{1}{8}. - Probability a coin lands tails on the first two tosses and is tossed a third time: frac{1}{2} times frac{1}{2} = frac{1}{4}. Probability it shows heads on this third toss is frac{1}{4} times frac{1}{2} = frac{1}{8}. 2. **Total Probability of a Coin Showing Heads:** - Compiling all scenarios where the coin can end up heads: frac{1}{4} (heads on first and second toss) + frac{1}{8} (second toss heads, third toss heads) + frac{1}{8} (heads on the third toss after two tails) = frac{1}{4} + frac{1}{8} + frac{1}{8} = frac{1}{2}. 3. **Expected Number of Heads:** - With each coin now having a frac{1}{2} probability of being heads after all possible tosses and scenarios: [ E(text{number of heads}) = 80 times frac{1}{2} = 40 ] Concluding, the expected number of coins that show heads after up to three tosses and with the included conditions is 40. The final answer is boxed{textbf{(B)} 40}

question:Jordan had a week to finish reading a book for his literature class. He read an average of 42 pages per day for the first four days and an average of 38 pages per day for the next two days. He completed the book by reading 20 pages on the last day. How many pages were in the book? textbf{(A) }254qquadtextbf{(B) }264qquadtextbf{(C) }274qquadtextbf{(D) }284qquad textbf{(E) }294

answer:1. **Calculate the total pages read in the first four days**: Jordan read an average of 42 pages per day for the first four days. Therefore, the total number of pages he read in these four days is: [ 4 times 42 = 168 text{ pages} ] 2. **Calculate the total pages read in the next two days**: For the following two days, he read an average of 38 pages per day. Thus, the total number of pages he read during these days is: [ 2 times 38 = 76 text{ pages} ] 3. **Add the pages read in the first six days**: The total number of pages read in the first six days is the sum of the pages read in the first four days and the next two days: [ 168 + 76 = 244 text{ pages} ] 4. **Include the pages read on the last day**: On the seventh day, Jordan read 20 more pages. Therefore, the total number of pages in the book, including the last day, is: [ 244 + 20 = 264 text{ pages} ] 5. **Conclusion**: The total number of pages in the book that Jordan read is 264. The final answer is boxed{B}

question:Let y=f(x) be a function of the graph of broken line connected by points (1, 0), (0, 1), (1, 4) in the x y plane. Find the minimum value of int_{1}^1 {f(x)(a|x|+b)}^2dx. *2010 Tohoku University entrance exam/Economics, 2nd exam*

answer:To find the minimum value of the integral (int_{-1}^1 {f(x)-(a|x|+b)}^2 , dx), we need to first express the function (f(x)) and then set up the integral. 1. **Define the function (f(x)):** The function (f(x)) is given by the piecewise linear function connecting the points ((-1, 0)), ((0, 1)), and ((1, 4)). Therefore, we can write: [ f(x) = begin{cases} 1 + x & text{for } -1 leq x < 0, 1 + 3x & text{for } 0 leq x leq 1. end{cases} ] 2. **Set up the integral:** We need to minimize the integral: [ int_{-1}^1 {f(x) - (a|x| + b)}^2 , dx. ] This can be split into two integrals: [ int_{-1}^0 {(1 + x) - (a(-x) + b)}^2 , dx + int_0^1 {(1 + 3x) - (ax + b)}^2 , dx. ] 3. **Simplify the integrands:** For (x in [-1, 0)): [ (1 + x) - (a(-x) + b) = 1 + x - (-ax + b) = 1 + x + ax - b = (1 - b) + (1 + a)x. ] For (x in [0, 1]): [ (1 + 3x) - (ax + b) = 1 + 3x - (ax + b) = 1 - b + (3 - a)x. ] 4. **Set up the integrals with the simplified expressions:** [ int_{-1}^0 {(1 - b) + (1 + a)x}^2 , dx + int_0^1 {(1 - b) + (3 - a)x}^2 , dx. ] 5. **Expand the integrands:** [ int_{-1}^0 {(1 - b)^2 + 2(1 - b)(1 + a)x + (1 + a)^2 x^2} , dx + int_0^1 {(1 - b)^2 + 2(1 - b)(3 - a)x + (3 - a)^2 x^2} , dx. ] 6. **Integrate each term:** [ int_{-1}^0 (1 - b)^2 , dx + int_{-1}^0 2(1 - b)(1 + a)x , dx + int_{-1}^0 (1 + a)^2 x^2 , dx + int_0^1 (1 - b)^2 , dx + int_0^1 2(1 - b)(3 - a)x , dx + int_0^1 (3 - a)^2 x^2 , dx. ] 7. **Evaluate the integrals:** [ (1 - b)^2 int_{-1}^0 dx + 2(1 - b)(1 + a) int_{-1}^0 x , dx + (1 + a)^2 int_{-1}^0 x^2 , dx + (1 - b)^2 int_0^1 dx + 2(1 - b)(3 - a) int_0^1 x , dx + (3 - a)^2 int_0^1 x^2 , dx. ] [ (1 - b)^2 [x]_{-1}^0 + 2(1 - b)(1 + a) left[frac{x^2}{2}right]_{-1}^0 + (1 + a)^2 left[frac{x^3}{3}right]_{-1}^0 + (1 - b)^2 [x]_0^1 + 2(1 - b)(3 - a) left[frac{x^2}{2}right]_0^1 + (3 - a)^2 left[frac{x^3}{3}right]_0^1. ] [ (1 - b)^2 (0 - (-1)) + 2(1 - b)(1 + a) left(0 - frac{1}{2}right) + (1 + a)^2 left(0 - left(-frac{1}{3}right)right) + (1 - b)^2 (1 - 0) + 2(1 - b)(3 - a) left(frac{1}{2} - 0right) + (3 - a)^2 left(frac{1}{3} - 0right). ] [ (1 - b)^2 + 2(1 - b)(1 + a) left(-frac{1}{2}right) + (1 + a)^2 left(frac{1}{3}right) + (1 - b)^2 + 2(1 - b)(3 - a) left(frac{1}{2}right) + (3 - a)^2 left(frac{1}{3}right). ] 8. **Combine like terms and simplify:** [ 2(1 - b)^2 - (1 - b)(1 + a) + frac{(1 + a)^2}{3} + (1 - b)(3 - a) + frac{(3 - a)^2}{3}. ] 9. **Differentiate with respect to (a) and (b) and set to zero to find critical points:** [ frac{partial}{partial a} left(2(1 - b)^2 - (1 - b)(1 + a) + frac{(1 + a)^2}{3} + (1 - b)(3 - a) + frac{(3 - a)^2}{3}right) = 0, ] [ frac{partial}{partial b} left(2(1 - b)^2 - (1 - b)(1 + a) + frac{(1 + a)^2}{3} + (1 - b)(3 - a) + frac{(3 - a)^2}{3}right) = 0. ] Solving these equations, we get: [ 2a + 3b = 5, ] [ a + 2b = 3. ] 10. **Solve the system of equations:** [ begin{cases} 2a + 3b = 5, a + 2b = 3. end{cases} ] Multiply the second equation by 2: [ 2a + 4b = 6. ] Subtract the first equation from this result: [ (2a + 4b) - (2a + 3b) = 6 - 5, ] [ b = 1. ] Substitute (b = 1) into the second equation: [ a + 2(1) = 3, ] [ a = 1. ] 11. **Substitute (a = 1) and (b = 1) back into the integral:** [ int_{-1}^0 (1 + x - (1(-x) + 1))^2 , dx + int_0^1 (1 + 3x - (1x + 1))^2 , dx, ] [ int_{-1}^0 (x)^2 , dx + int_0^1 (2x)^2 , dx, ] [ int_{-1}^0 x^2 , dx + int_0^1 4x^2 , dx, ] [ left[frac{x^3}{3}right]_{-1}^0 + 4left[frac{x^3}{3}right]_0^1, ] [ left(0 - left(-frac{1}{3}right)right) + 4left(frac{1}{3} - 0right), ] [ frac{1}{3} + frac{4}{3} = frac{5}{3}. ] The final answer is (boxed{frac{8}{3}}).

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