Question

In a class there are 15 boys and 20 girls. The teacher wants to
select a boy and a girl to represent the class in a function. In how many ways
can the teacher make this selection?

Answer 1

you have to have a idea of permutation 
so answer is 15 × 20 = 300 ways

Answer 2

there r 15*20=300ways to select one boys nd one girl