Permutation & Combination
2014-05-14 3:19 pm
There are nine cards each marked with 1 to 9. Now 6 cards are to be drawn from these 9 cards, find the no. of ways that the '3' and '4' card are either both included or both not included.
回答 (1)
2014-05-14 4:05 pm
✔ 最佳答案
both included:step 1, choose 2 cards from '3' and '4'. 2C2 ways
step 2, choose 4 cards from '1, 2, 5, 6, 7, 8, 9'. 7C4 ways
both not included:
step 1, choose 6 cards from '1, 2, 5, 6, 7, 8, 9'. 7C6 ways
Thus, the required no. of ways = 2C2 x 7C4 + 7C6 = 42
參考: knowledge
收錄日期: 2021-04-28 14:21:36
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20140514000051KK00029