I actually "solved" it in less than 2min

来源: 于 2012-12-28 19:07:24 [旧帖] [给我悄悄话] 本文已被阅读：次

I found this.

http://math.stackexchange.com/questions/261826/what-is-three-different-way-to-solve-this-probability-combinatorics-problem-of

刚开始以为您又要搞脑筋急转弯，故意把d改成了?d.