#### Answer

$\text{ approximately } 27 \text{ } mph$

#### Work Step by Step

Substituting $r=300,$ in the given function, $
V(r)=\sqrt{2.5r}
,$ results to
\begin{array}{l}\require{cancel}
V(r)=\sqrt{2.5(300)}
\\
V(r)=\sqrt{750}
.\end{array}
Using the properties of radicals, the equation above is equivalent to
\begin{array}{l}\require{cancel}
V(r)=\sqrt{25\cdot30}
\\
V(r)=\sqrt{5^2\cdot30}
\\
V(r)=5\sqrt{30}
\\
V(r)\approx27
.\end{array}
Hence, the maximum safe velocity, $V,$ is $
\text{ approximately } 27 \text{ } mph
.$