Question

The ratio of the number of boys to the number of girls in a class is $4:5$. If there are $20$ boys in the class, then the number of students in the class is

• A. $25$
• B. $30$
• C. $40$
• D. $45$

Answer 1

The correct option is D

$45$

Explanation for the correct option:

The number of boys in the class $=20$

Given, that the ratio of the number of boys to the number of girls in the class is $4:5$

$$\begin{gathered} \frac{Thenumberofboysintheclass}{Thenumberofgirlsintheclass}=\frac{4}{5} \\ \frac{20}{Thenumberofgirlsintheclass}=\frac{4}{5} \\ 4\times Thenumberofgirlsintheclass=20\times 5 \\ Thenumberofgirlsintheclass=\frac{20\times 5}{4}=25 \end{gathered}$$

Total number of students $=$ The number of boys in the class $+$ The number of girls in the class

Total number of students $=$ $20+25=45$

Therefore, the total number of students in the class is $45$.

Hence, option (D) is correct .