※ 引述《JimCroce (我要下五子棋 ￾N￾ )》之铭言： : 我在Ross的机率书写的一个题目 我不知道怎麽把答案合并成最後 卡住 : 题目 : An urn contains n white and m black balls. The balls are withdrawn : one at a time until only those of the same color are left. Show that with : probability n/(n+m) they are all white. : *Hint: Imagine that the experiment continues until all the balls are removed : and consider the last ball withdrawn. : 谢谢回答 请问 如果 从剩最後两颗是黑跟白开始想 N M ( ) ( ) N-1 M-1 -------------- * (1/2) M + N ( ) M+N-2 再来剩三颗两黑一白 N M ( ) ( ) N-1 M-2 ------------------ * (1/3) M+N ( ) M+N-3 ......算到全黑一白 N ( ) N-1 -------------------- *(1/M+1) M+N ( ) N 然後加总起来 请问我这样子的想法有错误嘛 最近一直想 只能想到这样 请高人帮我看一下~~~~谢谢 --

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