JEE Main Maths: Surface Areas and Volumes questions with solutions

Q1. A hollow (open) right circular cone has base radius R and vertical height H. What is its curved (lateral) surface area?

1. pi*R*sqrt(R² + H²)
2. pi*R²*sqrt(R² + H²)
3. 2*pi*R*sqrt(R² + H²)
4. pi*R*(R + H)

Answer: pi*R*sqrt(R² + H²)

The slant height is l = sqrt(R² + H²), and the curved surface area of a cone is pi*R*l, giving pi*R*sqrt(R² + H²).