[tex]\bf \qquad \qquad \textit{inverse proportional variation}
\\\\
\textit{\underline{y} varies inversely with \underline{x}}\qquad \qquad y=\cfrac{k}{x}\impliedby
\begin{array}{llll}
k=constant\ of\\
\qquad variation
\end{array}\\\\
-------------------------------[/tex]
[tex]\bf \textit{time it takes varies inversely with the speed rate}\qquad \stackrel{time}{t}=\cfrac{k}{\stackrel{rate}{r}}
\\\\\\
\textit{we also know that }
\begin{cases}
t=\stackrel{hrs}{4}\\
r=\stackrel{mph}{50}
\end{cases}\implies 4=\cfrac{k}{50}\implies 200=k
\\\\\\
\boxed{t=\cfrac{200}{r}}
\\\\\\
\textit{if your rate r = 40, what is your distance \underline{t}?}\qquad t=\cfrac{200}{40}[/tex]
