If the radius of a right circular cylinder is decreased by 10%, and the height is increased by 20%, then the percentage increase/decrease in its volume is:
Answer & explanation
Correct answer: option 4
We know that,
Volume of cylinder = π r2 h
We have,
If a radius is r and decreased bt 10% then it becomes = 90% of r
Also,h increased by 20% then height will be = 120% of h
Volume = π × 120% of h × 90% of r = 0.972πrh
Required percentage = (πrh - 0.972πrh) × \(\frac{1}{ πrh }\) × 100 = 2.8%