AMC 8 2016 Problem 21

AMC8 2016 年第 21 题

概率★★★★☆

A top hat contains 3 red chips and 2 green chips. Chips are drawn randomly, one at a time without replacement, until all 3 of the reds are drawn or until both green chips are drawn. What is the probability that the 3 reds are drawn?

一个罐子里装有 3 个红色筹码和 2 个绿色筹码。现在将筹码一个个随机抽出且不放回，直到 3 个红色筹码被全部取出或者 2 个绿色筹码被全部取出，这时取出动作立即停止，那么取出 3 个红色筹码的概率是多少？

A. $\dfrac{3}{10}$
B. $\dfrac{2}{5}$
C. $\dfrac{1}{2}$
D. $\dfrac{3}{5}$
E. $\dfrac{7}{10}$

正确答案 · Correct Answer

解析 · Solution

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