Question

A rectangular paper is folded into a cylinder. The length and breadth of the paper are L and B respectively. What is the outer surface area of the cylinder?

• A. $\pi$LB
• B. 2$\pi$LB
• C. LB
• D. 2LB

Answer 1

The correct option is C

LB

The cylinder is a 3-D object. To find its surface area, we need to convert it into a 2-D plane. Here the 3-D surface of cylinder can be unrolled into a 2-D rectangular sheet of paper. The area of the 3-D surface and that of the 2-D plane are the same.

It is clear that area of rectangle
= Length × Breadth
= LB