Probability of everyone having received work = (# of ways for everyone to have some work) / (# of ways to arrange the work) = (# of ways for 1 person getting 2 files + 2 people each getting 1 file) / (# of ways to distribute the 4 files) 作者: xiongxiong88 时间: 2006-6-26 13:15
4个科室共有一份文件是么作者: missouyang 时间: 2006-6-28 13:13
many thanks !!!!!!!
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