There were 121 children enrolled in the Cindy Dancing School in 2017. ⁵₁₁ of the children were boys. Additional children joined the dancing school in 2018. For every 5 boys who joined the dancing school, 4 girls joined the dancing school. If there was an equal number of girls and boys in 2018, how many girls joined the school in that year?

	Boys	Girls
Before	55	66
Change	+ 5 u	+ 4 u
After	55 + 5 u	66 + 4 u

Fraction of children who are girls
= 1 - ⁵₁₁
= ⁶₁₁

Number of boys at first
= ⁵₁₁ x 121
= 55

Number of girls at first
= ⁶₁₁ x 121
= 66

Boys who joined : Girls who joined
5 : 4

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

55 + 5 u = 66 + 4 u
5 u - 4 u = 66 - 55

1 u = 11

Number of girls who joined the school in that year
= 4 u
= 4 x 11
= 44

Answer(s): 44