2. 外语
  3. A typist types four envelopes and four letters. She places the letters in the envelopes at random. What are the chances that onl

A typist types four envelopes and four letters. She places the letters in the envelopes at random. What are the chances that onl

admin2013-02-03  40
问题 A typist types four envelopes and four letters. She places the letters in the envelopes at random. What are the chances that only three letters are in their correct envelopes?
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答案zero
解析 (如果三个都装对了，那么第四个也一定装对了，所以没有这种几率。)  
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本试题收录于： B类竞赛（英语专业本科专科）题库大学生英语竞赛（NECCS）分类
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B类竞赛（英语专业本科专科）

大学生英语竞赛（NECCS）

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