There were 220 children enrolled in the Jean Gym School in 2017. ⁴₁₁ of the children were girls. Additional children joined the gym school in 2018. For every 4 girls who joined the gym school, 3 boys joined the gym school. If there was an equal number of boys and girls in 2018, how many boys joined the school in that year?

	Girls	Boys
Before	80	140
Change	+ 4 u	+ 3 u
After	80 + 4 u	140 + 3 u

Fraction of children who are boys
= 1 - ⁴₁₁
= ⁷₁₁

Number of girls at first
= ⁴₁₁ x 220
= 80

Number of boys at first
= ⁷₁₁ x 220
= 140

Girls who joined : Boys who joined
4 : 3

The number of boys and girls in the end is the same.

80 + 4 u = 140 + 3 u
4 u - 3 u = 140 - 80

1 u = 60

Number of boys who joined the school in that year
= 3 u
= 3 x 60
= 180

Answer(s): 180