# If y varies inversely as x and y = 320 when x = 25, how do you find y when x is 40?

Jun 26, 2016

$y = 200$.

#### Explanation:

If $y$ is inversely as $x$, it means that it exists an equation like

$y = \frac{k}{x}$ where $k$ is a constant.

We know that when $x = 25$, $y = 320$, so we have

$320 = \frac{k}{25}$. From here we can calculate $k$ as

$k = 320 \cdot 25 = 8000$.

Then the equation is

$y = \frac{8000}{x}$.

We can now calculate $y = \frac{8000}{40} = 200$.