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标题: GWD1的一道概率题 [打印本页]

作者: cll0503 时间: 2009-5-22 16:29
标题: GWD1的一道概率题

Q37:

A jar contains 16 marbles, of which 4 are red, 3 are blue, and the rest are yellow. If 2 marbles are to be selected at random from the jar, one at a time without being replaced, what is the probability that the first marble selected will be red and the second marble selected will be blue?

A. 3/64

B. 1/20

C. 1/16

D. 1/12

E. 1/8

我是直接3/16乘以4/16算出来的，结果是A，但是正确答案是B，请问如何求出？

作者: cnzalieen 时间: 2009-5-22 17:25
第一次拿了一个就少了一个了所以第二次是15个的总数了4/16*3/15=1/20

作者: cll0503 时间: 2009-5-22 17:50

天，竟然是这样！

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