Question

$8$ is what percent of $40$?

Answer 1

When we say that something is $x$ percent of $y$, we mean that it is $y\times \frac{x}{100}$. So, if we say that $8$ is $x$ percent of $40$, that means that $8=40\times \frac{x}{100}$. Solving for $x$, we get
$8=40\times \frac{x}{100}$
$\Rightarrow 8=\frac{40x}{100}$
$\Rightarrow 8\times \frac{100}{40}=\frac{40x}{100}\times \frac{100}{40}$
$\Rightarrow 8\times \frac{5}{2}=x$
$\therefore x=20$
Thus $8$ is $20$ percent of $40$.