Use cylindrical shells to find the volume V of a right circular cone with height 7h and base radius 4r.

Answer 1

I don't see why you need calculus for this, nor why they are calling the height 7h and the radius 4r.

The differential volume of any cylindrical shell of radius r, height h and thickness dr is

2 pi r h dr

Integrating that from r = 0 to the outside radius R will give you the volume.