# The percent of boys in a class was 40%. How many students are there in the class?

Sep 20, 2017

To answer the question it necessary to know either the number of boys or the number of girls in the class.

Sep 20, 2017

A multiple of $5$

#### Explanation:

Percent means "per hundred", expressing a proportion.

The proportion of boys in the class is:

$\frac{40}{100} = \frac{2 \cdot \textcolor{red}{\cancel{\textcolor{b l a c k}{20}}}}{5 \cdot \textcolor{red}{\cancel{\textcolor{b l a c k}{20}}}} = \frac{2}{5}$

In other words, for every $5$ students in the class, $2$ are boys and $3$ are girls.

In order that the figure 40% be exact, the number of students must be a multiple of $5$.

Then the number of boys will be the corresponding multiple of $2$ and the number of girls the corresponding multiple of $3$.

That is about as much as we can deduce from the question as given.