From a solid cylindrical wooden block of height 18 cm and radius 7.5 cm, a conical cavity of the same height and same radius is taken out. What is the total surface area (in cm2) of the remaining solid?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 472.5 π.
The slant height of the cone =
CSA of Cylinder = 2πrh = 2π × 7.5 × 18 = 270π
CSA of cone = πrl = π × 7.5 × 19.5 = 146.25π.
Area of the base = πr2 = 56.25π.
TSA of the remaining solid = 270π + 146.25π + 56.25π = 472.5π.