4 boys and three girls are to be seated in a row in such a way that no two boys sit adjacent to each other. In how many different ways can it be done?

Explanation:

3 girls can be seated in a row in 3! ways.

Now, in the 4 gaps 4 BGBGBGB boys can be seated in 4! ways

Hence, the number of ways in which no two boys sit adjacent to each other

= 3!×4!=6×24=144