If y varies inversely as x and y = 12 when x = 3, how do you find x when y = 18?

Oct 1, 2016

$x = 2$

Explanation:

As $y$ varies inversely as $x$, $y \propto \frac{1}{x}$ or $y = k \times \frac{1}{x}$

i.e. $x \times y = k$

Hence as when x=3$,$y=12#, we have

$k = 3 \times 12 = 36$

and therefore when $y = 18$

we have $x \times 18 = 36$

or $x = \frac{36}{18} = 2$