[tex] \bf \textit{volume of a cone}\\\\
V=\cfrac{\pi r^2 h}{3}~~
\begin{cases}
r=radius\\
h=height\\
-----\\
V=108\pi \\
h=4
\end{cases}\implies 108\pi =\cfrac{\pi r^2(4)}{3}\implies 324\pi =4\pi r^2
\\\\\\
\cfrac{324\pi }{4\pi }=r^2\implies 81=r^2\implies \sqrt{81}=r\implies 9=r [/tex]
