2019 AMC 10B Problem 17


A red ball and a green ball are randomly and independently tossed into bins numbered with positive integers so that for each ball, the probability that it is tossed into bin kk is 2k2^{-k} for k=1,2,3,.k=1,2,3,\ldots. What is the probability that the red ball is tossed into a higher-numbered bin than the green ball?

(A) 14(B) 27(C) 13(D) 38(E) 37\textbf{(A) } \frac{1}{4} \qquad\textbf{(B) } \frac{2}{7} \qquad\textbf{(C) } \frac{1}{3} \qquad\textbf{(D) } \frac{3}{8} \qquad\textbf{(E) } \frac{3}{7}


Full credit goes to MAA for authoring these problems. These problems were taken on the AOPS website.

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Problem Tags: Counting and probability

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Category: AMC 10B
Points: 3
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