Tanya prepared 4 different letters to be sent to 4 different addresses. for each letter , she prepared an envelope with its correct address. if the 4 letters are to be put into the 4 envelopes at random, what is the probability that only 1 letter will be put into the envelope with its correct address?(I/3)作者: peiyangzhe 时间: 2007-6-21 14:02
这题被讨论过了，C41*（1+1）/P44
四封信有一封是对的，有四种情况
在一封是对的的情况下，剩下三封是错的，有两种情况
总共，24种情况
作者: ecsniffers 时间: 2007-6-21 20:41
对不起啊， 不知道这道题已经被讨论了, 你的讲解很清晰, 谢谢!
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