What is the number of ways that 4 boys and 3 girls can be seated so that boys and girls alternate?

120

144

The only pattern in which they can sit according to the given situation is,

BGBGBGB

Now boys can be arranged among themselves in 4! ways, and girls among themselves in 3! ways,

So total no. of ways

= 4 ! × 3 ! = 144