Question

In a school, 5/8 of the students are boys. If there are 240 girls, find the number of boys in the school.

Answer 1

n = number of students in the school

b = number of boys in the school

g = number of girls in the school

If 5 / 8 of the students are boys then:

1 - 5 / 8 = 8 / 8 - 5 / 8 = 3 / 8 of the students are girls.

b = 5 / 8 n

g = 3 / 8 n

There are 240 girls so:

g = 240

3 / 8 n = 240

Multiply both sides by 8

3 n = 1920

n = 1920 / 3 = 640

There are 640 students in a school.

b = 5 / 8 n = 5 / 8 ∙ 640 = 3200 / 8 = 400

There are 400 boys in a school.

Answer 2

total ---- x
boys ---- (5/8)x
girls ---- (3/8)x

(3/8)x = 240
x = 640

finish it up