Q3:

If a committee of 3 people is to be selected from among 5 married couples so that the committee does not include two people who are married to each other, how many such committees are possible?

A.     20

B.     40

C.     50

D.     80

E.      120

这道题我不知道错在哪儿咯，请大家帮忙看看哈.

我是这样算的:10*8*6=480种.答案为D.??

答案是啥？20？

 c10,3-8*5=80

我是这样理解的: 10个随便选3, c10,3=120, 然后减去couple同时被选的,

每一对 couple 被选后,剩下其他的8个任选1个,有8种

一共5对couples,5*8=40

不知有没有说对？

呵呵,谢谢提醒咯我想通咯~~按照我原先的思路正确算法应该是C5,3*C2,1*C2,1*C2,1=80，呜呜，这种题告中也曾困惑过我~~