# The ratio of boys to girls in an art class is 3:5 There are 12 boys in the class. How many girl are in the class?

Nov 30, 2016

$20 \text{ girls}$

#### Explanation:

We can solve this using fractions in ratio form.

Let x be the number of girls.

$\text{boys" rarr 3/12=5/x larr" girls}$

$\textcolor{b l u e}{\text{cross-multiply}}$

$\Rightarrow 3 x = \left(12 \times 5\right)$

$\Rightarrow 3 x = 60$

To solve for x, divide both sides by 3

$\frac{\cancel{3} x}{\cancel{3}} = \frac{60}{3}$

$\Rightarrow x = 20$

That is, there are 20 girls in the class.

Check : $\frac{12}{20} = \frac{3}{5} \text{ or } 3 : 5$