The area of the base of a right circular cone is 81π cm2 its height is 12 cm. What is curved surface area (in cm2) of the cone?

Answer: Option B

πr² = 81π
r = 9
Curved surface area of cone = πr$$l$$
$$l$$ = $$\sqrt{{12}^2+9^2}$$
$$l$$ = 15
Curved surface area = π × 9 × 15 = 135π