# If y = 7.2 when x = 10, what is the value of x when y = 20?

Aug 16, 2017

$y = 3.6$

#### Explanation:

It seems that the question refers to an inverse variation?

The constant in an inverse variation is found from $\textcolor{red}{k = x \times y}$

From this we can find $x \mathmr{and} y$, given the other one.

$x = \frac{k}{y} \mathmr{and} y = \frac{k}{x}$

$k = 7.2 \times 10 = 72$

therefore to find $y$:

$y = \frac{k}{x} = \frac{72}{20}$

$y = 3.6$