Question

the ratio of girls to boys in the sixth grade is 5:3. If there are 400 sixth graders, how many boys are there?

Answer 1

boys = 250

girls = 150

Explanation:

5g = 3b eq. 1

g + b = 400 eq. 2

g = girls

b = boys

From the eq. 2

g = 400 - b

Replacing this last eq. on eq. 1:

5(400-b) = 3b

5*400 + 5*-b = 3b

2000 - 5b = 3b

2000 = 3b + 5b

2000 = 8b

2000/8 = b

250 = b

From eq. 2

g + 250 = 400

g = 400 - 250

g = 150

Check:

from eq. 1

5*150 = 3*250 = 750