help thanks a lot!!

SHBILYB

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

ceciliading

答案是什么呀

macelino

C(2,1)*C(2,1)*C(2,1)*C(5,3)=2*2*2*5*4/2=80

[此贴子已经被作者于2008-1-27 23:43:28编辑过]

ceciliading

我算出来是D,但不是那么肯定,LZ在不,答案选啥啊

ceciliading

恩,和LS的一样,我用的是排除法做的,先10个里面取3个,然后再减去C(5,1)*C(8,1),同样是80

jczephyr

思路，先从5组选3组出来，C(5,3)

然后这三组中再分别2选1，

答案80，没错，限定性的组合问题，应该算是难题了。

东岸老男人

倒，在PREP里遇到一样的，唯一的不同是，不是5对，是从4对里面选3个人，那也应该是一样的算法吧.

结果是32？

brightcoolsz

1,c (10,3)- 5c(8,1) =120- 40 =80  费费一题和此类似

2, C(8,3)-4C(6,1)=56- 24 =32