Question

If the radius of the base of a right circular cone is 3r and its height is equal to the radius of the base, then its volume is

Options

• `1/3 pir^3`

• `2/3 pir^3`

• `3 pir^3`

• `9 pir^3`

Answer 1

The formula of the volume of a cone with base radius ‘r’ and vertical height ‘h’ is given as

Volume of cone =  `1/3 pi r^2 h`

Here it is given that the base radius is ’3r’ and that the vertical height is ‘3r’

Substituting these values in the above equation we get

Volume of cone = `1/3 pi(3r)^2(3r)`

= `9pir^3`