Question

In a class of 48 students the number of girls is three-fifth then the number of boys. The number of boys is
A. 25
B. 30
C. 35
D. 48

Answer 1

Hint: The total class can be written as sum of number of boys and girls or it can be represented as,
\[\text{Number of boys }+\text{ Number of girls }=\text{ 48}\].
Now as we know the number of girls is \[\dfrac{3}{5}\] of the number of boys so substitute it and hence find the number of boys.

Complete step-by-step answer:
In the question we are told that in a class of 48 students the number of girls is three-fifth then the number of boys. So, we have to find a number of boys.
So, we can write according to the question,
\[\text{Number of girls}=\dfrac{3}{5}\times \text{ number of boys}\text{.}\]
As we know that total strength of class which is 48. So we can also tell that the number of boys + number of boys is equal to 48.
Now we know that the number of girls is equal to \[\left( \dfrac{3}{5} \right)\] times the number of boys. So we can use it as,
Number of boy’s \[+\dfrac{3}{5}\] number of boys
\[\Rightarrow \text{number of boys}\left\{ 1+\dfrac{3}{5} \right\}\]
\[\Rightarrow \text{number of boys}\times \dfrac{8}{5}\]
Now we can say that the number of boys \[\times \dfrac{8}{5}\] can be written as 48.
So,
\[\dfrac{8}{5}\times number\text{ of boys=48}\]
we can also write,
\[Number\text{ of boys=48}\times \dfrac{8}{5}\]
Now on simplification we can say that the number of boys is 30.
Hence, the correct option is 'B'.

Note: We can take the number of boys as x. So, the number of girls will be \[\dfrac{3x}{5}\] hence, we can write \[x+\dfrac{3x}{5}=48\] and then solve for x to get the answer.