Question

If y varies inversely as x and y=3 when x=4, then y=12 when x=15

Please select the best answer from the choices provided

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F

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}`

`\bf \textit{we know that } \begin{cases} y = 3\\ x = 4 \end{cases}\implies 3=\cfrac{k}{4}\implies 12=k~\hfill \boxed{y=\cfrac{12}{x}} \\\\\\ \textit{when x = 15, what is \underline{y}?}\qquad y = \cfrac{12}{15}\implies y = \cfrac{4}{5}~\hfill \stackrel{\mathbb{FALSE}}{y\\e 12}`