Answer
$k=.14$, $y=\frac{.14}{x}$
Work Step by Step
If y varies inversely as x, we know that the variables x and y can be related by the function $y=\frac{k}{x}$, where k is the constant of proportionality.
If $y=.2$ when $x=.7$, then we know that $.2=\frac{k}{.7}$ (or $\frac{2}{10}=\frac{10k}{7}$). Multiply both sides by $\frac{7}{10}$.
$k=\frac{2\times7}{10\times10}=\frac{14}{100}=.14$
Therefore, the constant of variation is $k=.14$ and the inverse variation equation is $y=\frac{.14}{x}$.
