送交者: HunHunSheng 于 2008-07-31, 23:33:18:
回答: 两次出现(一次见面,一次电话)的都是男孩。 由 Amsel 于 2008-07-31, 23:24:33:
What is the probability your friend A has two boys?What is the probability your friend B has two boys?
加跟贴
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