The ratio of girls to boys in the grade is 7 to 8. If there are 140 girls, how many boys are there

there are 160 boys in the grade

There are 160 boys.

Set up a proportion:

the ratio of girls to boys is 7/8, we don't know how many boys there are but we know that there are 140 girls.

7/8 = 140/x

Make sure that girls and girls are across from each other in the proportion. 7 should be across from 140. 8 is across from x. X represents how many boys there are.

Solve for X (the amount of boys) and you get 160 boys.

And you can always check your answer by plugging it back into the problem.