AMC 8 2019 Problem 15

AMC8 2019 年第 15 题

概率★★★☆☆
On a beach, 50 people are wearing sunglasses and 35 people are wearing caps. Some people are wearing both sunglasses and caps. If one of the people wearing a cap is selected at random, the probability that this person is also wearing sunglasses is $2/5$. If instead, someone wearing sunglasses is selected at random, what is the probability that this person is also wearing a cap?
在一个沙滩上，50 人戴着太阳镜，35 人戴着帽子，有些人同时戴着太阳镜和帽子。如果从戴着帽子的人当中随机选一人，那么这个人同时也戴着太阳镜的概率是 。相反，如果从戴着太阳镜的人当中随机选择一人，那么这个人同时也戴着帽子的概率是多少？
  1. A.1485\displaystyle \frac{14}{85}
  2. B.725\displaystyle \frac{7}{25}
  3. C.25\displaystyle \frac{2}{5}
  4. D.47\displaystyle \frac{4}{7}
  5. E.710\displaystyle \frac{7}{10}

正确答案 · Correct Answer

B

解析 · Solution

解析整理中

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