In a school $\frac{4}{11}$ of the students are girls. If there are 490 boys. Find the number of girls.

Given:

In a school $\frac{4}{11}$ of the students are girls.

There are 490 boys. 

To do:

We have to find the number of girls.

Solution:

Let the total number of students in the school be $x$

Number of girls $=\frac{4}{11}\times x=\frac{4x}{11}$

This implies,

Number of boys $=x-\frac{4x}{11}$

$=\frac{11x-4x}{11}$

$=\frac{7x}{11}$
Therefore,

$\frac{7x}{11}=490$

$\Rightarrow 7x=490\times11$

$\Rightarrow x=70\times11=770$
 Number of girls in the school $=770-490=280$

The number of girls in the school is 280.