2. 外语
  3. There are 8 balls in a box, 2 of them are red, 4 of them are white, 2 of them are blue. If 2 balls are to be simultaneously and

There are 8 balls in a box, 2 of them are red, 4 of them are white, 2 of them are blue. If 2 balls are to be simultaneously and

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问题 There are 8 balls in a box, 2 of them are red, 4 of them are white, 2 of them are blue. If 2 balls are to be simultaneously and randomly selected, what is the probability that they will both be red?
选项 A、1/8
B、1/28
C、1/4
D、3/14
E、1/2
答案B
解析 同时取出两个球共有C82=28种方法，而两个球都为蓝球只有一种取法，所以所求概率为1/28。
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