# R is inversely proportional to the cube of S, if R = 2 and S = 7, how do you find the value of k?

Sep 29, 2015

$k = 686$

#### Explanation:

If $R$ is inversely proportional to the cube of $S$
$\textcolor{w h i t e}{\text{XXX}} R {S}^{3} = k$ for some constant $k$

Given that $R = 2$ and $S = 7$ is a solution to this equation,
we have
$\textcolor{w h i t e}{\text{XXX}} 2 \cdot {7}^{3} = k$
$\rightarrow \textcolor{w h i t e}{\text{XX}} k = 686$