Question

The volume of a certain right circular cone is 30 cubic inches. What is the volume, in cubic inches, of a second right circular cone with half the radius and twice the height of the first cone

Answer 1

V = 15 in.³

Explanation:

The original cylinder has radius r and height h.

V = πr²h

Its volume is 30 in.³, so

πr²h = 30 in.³

The new cylinder has radius (1/2)r and height 2h.

Its volume is

V = π(r/2)²(2h)

V = πr² × 2h/4

V = πr²h/2

πr²h is the volume of the original cylinder, and it is 30 in.³.

V = 30 in.³/2

V = 15 in.³