Question

The volume of a cylinder is 81 ft3. The volume of a cube is 42 ft3. What is the difference between the volume of a cone that fits exactly inside the cylinder and the volume of a pyramid that fits exactly inside the cube?

Answer 1

I already know this:
Cylinder:
V = pi x r^2 x h cylinder
Cone:
V = 1/3 pi x r^2 x h

But how do I do the problem if they only give me the volume?