GWD4-5

evelyn205205 · 发表于 2011-2-4 16:58:17

A certain club has 20 members.What is the ratio of the number of 5-member committees that can be formed from the members of the club to the number of 4-member committees that can be formed from the members of the club?

A.16 to 1
B.15 to 1
C.16 to 5
D.15 to 6
E.5 to 4
答案是C，我选的是A，是我的理解有误么？ratio=5p20/4p20？是这样算么？

kazemi · 发表于 2011-2-5 01:45:57

用组合，不是排列

C(20, 5)/C(20, 4)=16/5

evelyn205205 · 发表于 2011-2-5 10:35:14

用组合，不是排列

C(20, 5)/C(20, 4)=16/5

-- by 会员 kazemi (2011/2/5 1:45:57)

为啥一定是组合呢？
从20个人里面选5个或4个人来组成委员会，为什么不是排列的问题呢？

GWD4-5

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