The volume of a cylinder is equal to [tex]\frac{1}{3}\pi r^{2} h[/tex], where r is the radius of the cylinder and h is its height.
324 = [tex]\frac{1}{3}\pi r^{2} h[/tex]
324 = [tex]\frac{1}{3}[/tex] x 3.14 x [tex]r^{2}[/tex] x 1
309.55 = [tex]r^{2}[/tex]
r = [tex]\sqrt{309.55}[/tex]
r = approx. 17.59 inches
I hope this answer helped you! If you have any questions, feel free to ask away.