# Ex.8.1 Q3 Comparing Quantities - NCERT Maths Class 8

## Question

\(72\%\) of \(25\) students are interested in mathematics. How many are not interested in mathematics?

## Text Solution

**What is known?**

Total number of students \(= 25\)

Percentage of students who are interested in Mathematics \(= 72\%\)

**What is unknown?**

Number of students who are not interested in Mathematics

**Reasoning:**

Percentage is a special ratio that compares any quantity to \(100,\) with \(100\) representing one whole.

**Steps:**

Percentage of students who are not interested in Mathematics

\[\begin{align}& = \left( {100-72} \right)\%\\&= 28\% \end{align}\]

Therefore, number of students who are not good in Mathematics

\(\begin{align}&= 28\%\,\text{of the total number of students}\\&= 28\% \,\text{of} \,25 \\&= \frac{{{28}}}{{{100}}}{ \times 25}\\&=\frac{{{28}}}{{4}}\\& = 7\end{align}\)

The total number of students who are not interested in Mathematics are \(7.\)