标题:
a JJ question
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作者:
kay
时间:
2002-9-29 11:59
标题:
a JJ question
一个排列组合,说一个人去银行,花店,鞋店,还有一个什么地方,总共四个地方,要保证去银行在去花店之前,问总共有几种走法。
A: p44/2
I don't understand why divided by 2? Thanks very much!
作者:
twinhead
时间:
2002-9-29 12:22
因为全排列可分为“先银行后花店”和“先花店后银行”两种,且各为总排列的1/2
作者:
kay
时间:
2002-9-30 10:04
Thanks very much!
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