Question

There are 20 boys in a class and the ratio of the number of boys to the total number of students is 1 : 3. Find the ratio of the number of girls to the total number of students.

• A. 3 : 2
• B. 2 : 3
• C. 3 : 4
• D. 4 : 3

Answer 1

The correct option is B 2 : 3

Given, number of boys = 20
and, ratio of the number of boys to the total number of sudents = 1 : 3

Let the total number be x.
$\Rightarrow 1:3::20:x$
$\Rightarrow \frac{1}{3}$ = $\frac{20}{x}$
$\Rightarrow x=20\times \frac{3}{1}$
$\Rightarrow x=60$
$\therefore$ Number of girls
= total number of students - number of boys
= 60 - 20
= 40

So, ratio of number of girls to the total number of students
$=40:60=\frac{40}{60}=\frac{2}{3}=2:3$