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

admin2013-01-10  52

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?

选项

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。)
转载请注明原文地址:https://kaotiyun.com/show/jAAK777K
0

最新回复(0)