Question

Calculate the number of ways in which three girls and four boys can be seated on a row of seven chairs if each is to be symmetrical.

Answer 1

because there are an odd number of girls, they must sit in the middle 3 chairs to be symmetrical. the boys sit in the other 4 chairs.
There are 3! = 6 ways to arrange the girls and 4! = 24 ways to arrange the boys
6*24=144