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question:A biased coin lands heads with a probability of frac{2}{3} and tails with frac{1}{3}. A player can choose between Game C and Game D. In Game C, the player tosses the coin five times and wins if either the first three or the last three outcomes are all the same. In Game D, she tosses the coin five times and wins if at least one of the following conditions is met: the first two tosses are the same and the last two tosses are the same, or the middle three tosses are all the same. A) Game C has a higher probability of frac{5}{81} over Game D. B) Game D has a higher probability of frac{5}{81} over Game C. C) Game C has a higher probability of frac{29}{81} over Game D. D) Game D has a higher probability of frac{29}{81} over Game C.
answer:Game C: The player wins Game C if either the first three or the last three tosses are all the same. Calculate each separately: 1. Probability of first three tosses being the same (all heads or all tails): [ left(frac{2}{3}right)^3 + left(frac{1}{3}right)^3 = frac{8}{27} + frac{1}{27} = frac{9}{27} = frac{1}{3} ] 2. Probability of last three tosses being the same (similar calculation as the first three): [ frac{1}{3} ] 3. Adjust for overlap (first three and last three are the same), which is first three and last three all heads or all tails: [ left(frac{2}{3}right)^5 + left(frac{1}{3}right)^5 = frac{32}{243} + frac{1}{243} = frac{33}{243} = frac{11}{81} ] 4. Total probability of winning Game C: [ frac{1}{3} + frac{1}{3} - frac{11}{81} = frac{27}{81} + frac{27}{81} - frac{11}{81} = frac{43}{81} ] Game D: 1. Probability first two and last two tosses are the same: [ left(left(frac{2}{3}right)^2 + left(frac{1}{3}right)^2right)^2 = left(frac{4}{9} + frac{1}{9}right)^2 = left(frac{5}{9}right)^2 = frac{25}{81} ] 2. Probability of middle three tosses being the same: [ left(frac{2}{3}right)^3 + left(frac{1}{3}right)^3 = frac{9}{27} = frac{1}{3} ] 3. Adjust for overlap: [ left(left(frac{2}{3}right)^4 + left(frac{1}{3}right)^4right) times 2 = 2left(frac{16}{81} + frac{1}{81}right) = frac{34}{81} ] 4. Final probability for Game D: [ frac{25}{81} + frac{27}{81} - frac{34}{81} = frac{18}{81} = frac{2}{9} ] # Conclusion: text{Game C} has a higher probability of winning than text{Game D} since frac{43}{81} is greater than frac{2}{9}. The final answer is C) Game C has a higher probability of boxed{frac{29}{81}} over Game D.
question:For any positive integer mge2 define A_m={m+1, 3m+2, 5m+3, 7m+4, ldots, (2k1)m + k, ldots} . (1) For every mge2 , prove that there exists a positive integer a that satisfies 1le a<m and 2^ain A_m or 2^a+1in A_m . (2) For a certain mge2 , let a, b be positive integers that satisfy 2^ain A_m , 2^b+1in A_m . Let a_0, b_0 be the least such pair a, b . Find the relation between a_0 and b_0 .
answer:# Part (1) To prove that for every ( m ge 2 ), there exists a positive integer ( a ) that satisfies ( 1 le a < m ) and ( 2^a in A_m ) or ( 2^a + 1 in A_m ): 1. **Expression for ( 2^a in A_m )**: - We need to find a positive integer ( k ) such that ( 2^a = (2k-1)m + k ). - This can be rewritten as: [ 2^a = (2m+1)k - m ] - Rearranging, we get: [ 2^a + m equiv 0 pmod{2m+1} ] - This implies: [ 2^{a+1} + 2m equiv 0 pmod{2m+1} ] - Therefore: [ 2^{a+1} equiv 1 pmod{2m+1} ] 2. **Existence of ( a )**: - By Euler's theorem, ( 2^{varphi(2m+1)} equiv 1 pmod{2m+1} ). - Thus, we can take ( a = varphi(2m+1) - 1 geq 1 ). - Let ( a_0 ) be the least such ( a ), then: [ 2^{a_0+1} equiv 1 pmod{2m+1} ] 3. **Expression for ( 2^b + 1 in A_m )**: - We need to find a positive integer ( ell ) such that ( 2^b + 1 = (2ell-1)m + ell ). - This can be rewritten as: [ 2^b + 1 = (2m+1)ell - m ] - Rearranging, we get: [ 2^b + m + 1 equiv 0 pmod{2m+1} ] - This implies: [ 2^{b+1} + 2m + 2 equiv 0 pmod{2m+1} ] - Therefore: [ 2^{b+1} equiv -1 pmod{2m+1} ] 4. **Existence of ( b )**: - Let ( b_0 ) be the least such ( b ), then: [ 2^{b_0+1} equiv -1 pmod{2m+1} ] # Part (2) To find the relation between ( a_0 ) and ( b_0 ): 1. **Contradiction if ( a_0 < b_0 )**: - If ( a_0 < b_0 ), then: [ 2^{(b_0-a_0-1)+1} equiv -1 pmod{2m+1} ] - This contradicts the minimality of ( b_0 ). 2. **Contradiction if ( b_0 < a_0 < 2b_0+1 )**: - If ( b_0 < a_0 < 2b_0+1 ), then: [ 2^{(a_0-b_0-1)+1} equiv -1 pmod{2m+1} ] - This again contradicts the minimality of ( b_0 ). 3. **Conclusion**: - We clearly have: [ 2^{2(b_0+1)} equiv 1 pmod{2m+1} ] - Thus: [ a_0 = 2b_0 + 1 ] # Justification for ( m ge 2 ): 1. **Case when ( a_0 < varphi(2m+1)-1 )**: - If ( a_0 < varphi(2m+1)-1 ), then: [ a_0 leq frac{1}{2}varphi(2m+1) - 1 leq m-1 ] - This satisfies ( 1 le a < m ). 2. **Case when ( a_0 = varphi(2m+1)-1 )**: - If ( 2m+1 ) has at least two distinct prime factors, then: [ 2m+1 = pq ] - Using properties of Euler's totient function and multiplicative order, we get a contradiction unless ( 2m+1 ) is a power of a prime. 3. **Conclusion**: - For ( m ge 2 ), the relation ( a_0 = 2b_0 + 1 ) holds, and the restriction ( m ge 2 ) avoids exceptions. (blacksquare) The final answer is ( boxed{ a_0 = 2b_0 + 1 } )
question:A wheel is divided into four equal regions labeled E, F, G, and H. The probability that the spinner stops on region E is frac{1}{2}, and the probability of stopping on region F is frac{1}{4}. The probability of the wheel stopping on region G is double that of it stopping on region H. What is the probability of the spinner stopping in region G? Express your answer as a common fraction.
answer:Let y be the probability of the spinner stopping on region G, and let z be the probability of stopping on region H. According to the problem, y = 2z. The total probability for all four regions must sum to 1: [ frac{1}{2} + frac{1}{4} + y + z = 1 ] Since y = 2z, we substitute y with 2z in the equation: [ frac{1}{2} + frac{1}{4} + 2z + z = 1 ] [ frac{3}{4} + 3z = 1 ] Solving for z: [ 3z = 1 - frac{3}{4} ] [ 3z = frac{1}{4} ] [ z = frac{1}{12} ] Since y = 2z, we find y: [ y = 2 cdot frac{1}{12} = frac{1}{6} ] Thus, the probability of the spinner stopping in region G is boxed{frac{1}{6}}.
question:The pages of a book are numbered 1 through n. A page number from the book was erroneously added twice resulting in an incorrect sum of 3050. Identify the page that was added twice.
answer:If all the page numbers were summed correctly, the equation would be: [1 + 2 + cdots + n = frac{n(n + 1)}{2}] Given that one page number was added twice, the total sum is incorrect, indicated as 3050, so the correct sum should fall somewhere between: [frac{n(n+1)}{2} + 1 text{ and } frac{n(n+1)}{2} + n] We are to find the value of n such that: [frac{n(n+1)}{2} + 1 leq 3050 leq frac{n(n+1)}{2} + n] To approximate n, consider that: [frac{n(n+1)}{2} approx 3050] [n(n+1) approx 6100] [n^2 + n - 6100 approx 0] Using the quadratic formula: [n = frac{-1 pm sqrt{1 + 24400}}{2} = frac{-1 pm 157}{2}] Thus, n approx frac{156}{2} = 78 (only considering the positive root). For n = 78: [frac{n(n+1)}{2} = frac{78(79)}{2} = 3081] It appears this value is slightly too large. Let's try n = 77 next: [frac{77(78)}{2} = 3003] This works because: [3003 + 1 leq 3050 leq 3003 + 77] Thus, 3050 - 3003 = boxed{47}.