The 4 beads in a bag are identical except that 2 are red and 2 are blue. If 2 beads are to be simultaneously and randomly select

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问题 The 4 beads in a bag are identical except that 2 are red and 2 are blue. If 2 beads are to be simultaneously and randomly selected, what is the probability that they will both be blue?

选项 A、1/6
B、1/4
C、1/3
D、1/2
E、5/6

答案A

解析 一个袋子中有4个相同的珠子,其颜色为2红2蓝。若同时随机地取出2个珠子,问这两个珠子同为蓝色的概率是多少?
解:本题的正确答案为(A)。第一个珠子为蓝色的概率是2/4,第二个仍为蓝色的概率是1/3,所以两个同为蓝色的概率是:P=2/4×1/3=1/6
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