4 boys and 3 girls are to be seated in 7 chairs such that no two boys are together. In how many ways can this be done?

1 Answer

144

Explanation:

Notice that the only way to have two boys not sitting next to each other requires that the seating be:

B G B G B G B

There are 4! = 24 ways to sit the boys in the boy seats and 3! = 6 ways to sit the girls in the girl seats. This gives:

24xx6=144 ways the boys and girls can sit.