#### Answer

$\color{blue}{y=\frac{0.0015}{x^2}}$.

#### Work Step by Step

RECALL:
(1) When $y$ varies directly as $x$, the variation is direct and is represented by the equation $y=kx$ where $k$ is the constant of variation.
(2) When $y$ varies inversely as $x$, the variation is inverse and is represented by the equation $y=\frac{k}{x}$ where $k$ is the constant of variation.
$y$ varies inversely as the square of $x$ so the equation is $y=\frac{k}{x^2}$ with $k$=constant of variation. To find the value of $k$, substitute the given values into $y=\frac{k}{x^2}$ to obtain:
$$y=\frac{k}{x^2}
\\0.15=\frac{k}{0.1^2}
\\0.15 =\frac{k}{0.01}
\\0.15(0.01)=k
\\0.0015=k$$
Thus, the equation of the variation is: $\color{blue}{y=\frac{0.0015}{x^2}}$.