[tex]\bf \textit{volume of a cone}\\\\
V=\cfrac{\pi r^2 h}{3}\qquad
\begin{cases}
r=radius\\
h=height\\
-----\\
V=12\\
h=3
\end{cases}\implies 12=\cfrac{\pi \cdot r^2\cdot 3}{3}
\\\\\\
12=\pi r^2\implies \cfrac{12}{\pi }=r^2\implies \sqrt{\cfrac{12}{\pi }}=r[/tex]
