Answer:



Step-by-step explanation:
The volume of the cylinder is

where r is the radius of a base circle and h is the cylinder's height.
If cylinder has diameter of 8 inches, then its radius is 4 inches. The height of the cylinder is 5 inches. Thus, the volume of the cylinder is

The volume of the cone is

where r is the radius of a base circle and h is the cone's height.
If cone has diameter of 8 inches, then its radius is 4 inches. The height of the cone is 15 inches. Thus, the volume of the cone is

As you can see the cylinder and the cone have the same volume.