If 30% of a class consists of boys and the number of boys in the class is fifteen, how many girls are there in the class?

Answer 1

If 30% of the class is 15 boys, then 100% of the class is:

15 ÷ 0.30 = 50 students total

Now subtract the boys to find the number of girls:

50 - 15 = 35 girls

Answer 2

We need to represent the number of students in the whole class, so we will call the total number of students in the whole class N.

The boys represent 30% of N, and there are 15 boys.

So first change the 30% to 0.30, then we have

0.30 * N = 15 boys (30% of the total kids in class = 15 boys)

So divide both sides by 0.30 and find that N = 50 (there are 50 students in the whole class)

If a student is not a boy, the student is a girl, so 50 - 15 = 35 girls.