A committee of 5 is to be chosen from a group of 9 people.The probability that a certain married couple will serve either together or not at all?
4/9
If the couples serve then 3 people can be selected in 7C3 ways.
If the couples don't serve then 5 people can be selected in 7C5 ways.
Favourable case: 7C3+7C5−−−(1)
Sample Space: 9C5−−−(2)
P(E)=(1)(2)
P(E)=49