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

• A. $\frac{1}{3}\pi r^3$
• B. $\frac{2}{3}\pi r^3$
• C. $3\pi r^3$
• D. $9\pi r^3$

Answer 1

The correct option is D

$9\pi r^3$

$Radiusofthebaseofacone\left(R\right)=3randheight\left(H\right)=3r\therefore Volume=\frac{1}{3}\pi R^{2}H=\frac{1}{3}\pi \times (3r{)}^2\times 3r=\frac{1}{3}\pi \times 9r^2\times 3r=9\pi r^3$