作者aaaaaakoyasu (六点半天色还没亮)
看板GMAT
标题[计量] PP1-PS
时间Thu Nov 6 12:51:02 2008
A certain law firm consists of 4 senior partners and 6 junior partners. How
many different groups of 3 partners can be formed in which at least one
member of the group is a senior partner? (Two groups are considered
different if at least one group member is different.)
(A) 48
(B) 100
(C) 120
(D) 288
(E) 600
At least one member of the group is a senior partner 有两种算法
一：所有组合 减 组合都是junior 这我算出来是100 也是正确答案
二；三人团体中 一人是senior的组合 + 两人是senior的组合 + 三人是senior的组合
(4x6x5)/3! + (4x3x6)/3! + (4x3x2)/3! = 36 不是100
第二个算法有哪边错了吗？
因为图书馆要关了，一直找不到哪边思考错误...
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