回复：回复：依次任取7个小于等于10的正整数，求其和为20的概率？

来源: 于 2010-06-07 10:01:11 [旧帖] [给我悄悄话] 本文已被阅读：次

agree- seems to be a 体力活 to me too. did not a see shortcut solution.

my estimated result is about~ 0.3%.