If the height of a cylinder is increased by 15% and the radius of its base is decreased by 10% then the percentage change in its curved surface area is :

Answer: Option B

Increase in height = 15% = $$\frac{3}{20}$$
Decrease in base radius = 10% = $$\frac{1}{10}$$

	Initial	Final
Radius	10	9
height	20	23
Area	200	207

Increment in Area = 207 - 200 = 7
Required % increase in area
= $$\frac{7}{200}$$ × 100
= 3.5%