Question

A grade has 81 girls and 72 boys. The grade is split into groups that have the same ratio of girls to boys as the whole grade. How many girls are in a group that has 16 boys?

Answer 1

There will be 18 girls in a group of 16 boys.

you divide 72 by 16 and get 4.5.
then you divide 81 by 4.5 and get 18.

That is how you get 18 girls in a  group of 16 boys.

Hope that helped.