If the ratio of boys to girls is 12 : 5, and the total number of girls is 840. How many boys are there?

Given:

The ratio of boys to girls $= 12 : 5$.

The total number of girls $=840$.

To do:

We have to find the number of boys.

Solution:

Let the number of boys be $x$.

Therefore,

$12:5=x:840$

$\frac{12}{5}=\frac{x}{840}$

$x=\frac{840\times12}{5}$

$x=168\times12$

$x=2016$

The number of boys is $2016$.