The are of the base of a right circular cone is 81 π cm2 and its height is 12 cm. What is the curved surface area (in cm2) of the cone?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 135π
Concept
CSA of cone = π x r x l
Application
Area of Base = π x r2 = 81π
r2 = 81
r = 9cm
Height = 12 cm
Slant Height = √(r2 + h2)
Putting the values of r and h
l = √(81 + 144)
l = 15 cm
CSA of cone = π x r x l
π x 9 x 15 = 135 π