Question

 The sum of the number of boys and girls in a school is 150. If the number of boys is x, then the number of girls becomes x% of the total number of students. The number of boys is:
A. 40
B. 50
C. 60
D. 90

Answer 1

Hint: We know the value of total number of students, so we will convert the number of girls from percentage to number and then we will add the number of girls and the number of boys and we will equate it to the total number of students.

Complete step by step answer:
Let’s start our solution by converting the percentage of girl into number,
To convert percentage into number we have divided the given percentage by 100 and then we have to multiply it by the total number of students.
X% of girls = $\dfrac{x}{100}\times 150$
Now we know the value of the number of girls and number of boys, we will add those two values and equate it to 150.
$\begin{align}
  & x+\dfrac{3x}{2}=150 \\
 & \dfrac{5x}{2}=150 \\
 & x=60 \\
\end{align}$
Hence, the number of boys in the school is 60 and the number of girls is 90.
So, the correct answer is option (c).

Note: Here we have converted the number of girls from percentage to number, the method that we have used for the conversion should be kept in mind, one might make mistakes by taking the given percentage as the number of girl students which will lead to wrong answers.