Answer
$6\sqrt {5}$ miles or $13.4$ miles.
Work Step by Step
The given function is
$d(x)=\sqrt {\frac{3x}{2}}$
The value of $x$ is $120$
Plug into the function.
$d(120)=\sqrt {\frac{3(120)}{2}}$
Simplify.
$d(120)=\sqrt {3\cdot 60}$
$d(120)=\sqrt {3^2\cdot5\cdot2^2}$
$d(120)=3\cdot 2\sqrt {5}$
$d(120)=6\sqrt {5}$
Use a calculator to solve.
$d(120)=13.416407865$
Round to the nearest tenth of a mile.
$d(120)=13.4$
