The ratio of girls to boys is 2:3 and there are 20 people in the class, how many are girls and boys?

1 Answer
Jun 2, 2015

Lets name b the number of boys and g the number of girls
b+g=20
g/b=2/3 so g=(2b)/3 ( we multiply by b on each side )

We can thus replace g in the equation :

b+(2b)/3=20

We want to put on the same denominator :

(3b)/3+(2b)/3=20

(5b)/3=20

5b=60 ( we multiply by 3 on each side )
b= 12 ( we divide by 5 on each side )

We can thus now find g :

b+g=20
12+g=20
g=20-12 ( we substract 12 on each side )
g=8

There are thus 12 boys and 8 girls in the class