In a class the ratio of boys to girls is $4 : 5$. After 8 boys move to another section, the ratio becomes $2 : 3$. How many girls are in the class?

Explanation

1. 01

   Let boys = 4x and girls = 5x.

2. 02

   $\frac{4x - 8}{5x} = \frac{2}{3}$ gives $12x - 24 = 10x$, so $x = 12$.

3. 03

   Girls = $5 \times 12 = 60$.