Question

If $Y$ varies inversely as $x$ and if $y=4$ when $x=72$. Find the value of $y$ when $x=9$.

Answer 1

$\begin{array}{c}y\times \frac{1}{x}\\ y=\frac{k}{x}\\ whenx=72,y=4\\ 4=\frac{k}{72}\\ k=4\times 72\\ k=288\\ y=\frac{288}{x}\\ putx=9\\ y=\frac{288}{9}=32\\ y=32\end{array}$