Question : If the radius of the base, and the height of a right circular cone are increased by 20%, what is the approximate percentage increase in volume?
Option 1: 60
Option 2: 68.8
Option 3: 72.8
Option 4: 75
Correct Answer: 72.8
Solution :
Let the base radius and height of the cone be r and h respectively
Then, volume =
If base radius is increased 20 %, new radius =
Similarly, New height =
New volume =
Hence, percentage increase =
Hence, the correct answer is 72.8.