k people go to a restaurant for dinner.
Each puts an umbrella into a bin.
When they leave, each of them randomly takes one umbrella.
What is the expected number of the people who get their own umbrellas?
Question ab prob.
2010-05-02 8:35 am
回答 (2)
2010-05-02 6:04 pm
✔ 最佳答案
=====================================================圖片參考：http://img19.imageshack.us/img19/2024/29093398.png
2010-05-02 10:04:25 補充：
http://img19.imageshack.us/img19/2024/29093398.png
2010-05-02 9:45 am
收錄日期: 2021-04-23 23:27:59
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20100502000051KK00056