Question:
A closet contains n pairs of shoes. If 2r shoes are chosen at random (r<n), what is the probability that there will be no matching pair in the sample?
Probability
2011-03-10 2:06 am
回答 (1)
2011-03-10 2:19 am
✔ 最佳答案
Solution:Total combinations : 2nC2r
Imagine that each pair of shoes has unique colour. Then the colours of these 2r shoes should be different. The no. of choices of colours is nC2r with 2 choices for the shoe of each special colour.
Probability
= (nC2r)(2^2r)/(2nC2r)
收錄日期: 2021-04-26 14:04:41
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20110309000051KK00731