Question

Suppose that y varies inversely as x and that y=8 when x=3. Calculate the value of y when x= 10.

Answer 1

$\bf \qquad \qquad \textit{inverse proportional variation} \\\\ \textit{\underline{y} varies inversely with \underline{x}} ~\hspace{6em} \stackrel{\textit{constant of variation}}{y=\cfrac{\stackrel{\downarrow }{k}}{x}~\hfill } \\\\[-0.35em] \rule{34em}{0.25pt}\\\\ \textit{we know that } \begin{cases} y = 8\\ x = 3 \end{cases}\implies 8=\cfrac{k}{3}\implies 24=k~\hfill \boxed{y = \cfrac{24}{x}} \\\\\\ \textit{when x = 10, what is \underline{y}?}\qquad \qquad y = \cfrac{24}{10}\implies y = \cfrac{12}{5}$