EXPLANATION
If the volume of the cylinder is 81pi cubic centimeters and the radius is 3cm, the height would be given by the following equation:
[tex]Volume=\pi\cdot r^2\cdot h[/tex]Replacing terms:
[tex]81\pi=\pi\cdot3^2\cdot h[/tex]Isolating h:
[tex]\frac{81\pi}{\pi3^2}=h[/tex]Simplifying:
[tex]9=h[/tex]The height is 9 centimeters.