Answer:
[tex]2160\pi \:\mathrm{ft^3} \approx 6786\:\mathrm{ft^3}[/tex]
Step-by-step explanation:
The volume of a cylinder is given as:
[tex]r^2\pi\cdot h[/tex].
Thus, the difference of the cylinders' volumes are:
[tex]|18^2\cdot 20\cdot \pi - 12^2\cdot 30 \cdot \pi|\approx \fbox{$6785.84\:\mathrm{ft^3}$}[/tex].
Since you've said [tex]6785.8[/tex] is not being accepted as an answer, please check all instructions to see if there are directions asking you to specifically round your answer. If not, you can ask your teacher/instructor what they're looking for.
