How many ways can a committee of nine be formed from 10 men and their wives, if no husband serves on it with his wife?

5120

Step-by-step explanation:

divide the entire group into 10 groups where each group has a man and his wife.

number of ways of selecting 9 groups is 10C9 which equals 10 ways

the number of ways selecting 1 person from a group is 2C1 = 2.

So that means the number of ways of selecting 1 person from 9 groups is 2^9=512

number of ways to form the committee is 10*2^9=5120