Question

The radius and height of a cone are each increased by $20$, then the volume of the cone is increased by

• A. $20$
• B. $40$
• C. $60$
• D. $72.8$

Answer 1

The correct option is D $72.8$

Let, the radius and height of the cone = $r$ and $h$

Volume of the cone =$\pi r^2.h$

Percentage increased in radius,

$20+20+\frac{40\times 20}{100}=40+4=44$

Height is h which is 20% increased,

Now,

Net percentage change in volume of cone,

$=44+20+\frac{40\times 20}{100}$

$=64+8.8=72.8$

Hence, this is the answer.