Question

There are 36 members in a student council in a school and the ratio of the number of boys to the number of girls is 3 : 1. How any more girls should be added to the council so that the ratio of the number of boys to the number of girls may be 9 : 5?

Answer 1

A ratio of number of boys to the number of girls = 3 : 1

Let the number of boys be 3x and the number of girls be x.

∴ 3x + x = 36

4x = 36

x = 9

∴ Number of boys = 27

Number of girls = 9

Le n number of girls be added to the council.

From given information, we have:

${\displaystyle \frac{27}{9+n}=\frac{9}{5}}$

135 = 81 + 9n

9n = 54

n = 6

Thus, 6 girl are added to the council.