Question

A right circular cylinder just encloses a sphere of radius r (see figure). Find the curved surface area of the cylinder.

• A. $3\pi r^2$
• B. $12\pi r^2$
• C. $9\pi r^2$
• D. $4\pi r^2$

Answer 1

The correct option is D

$4\pi r^2$

Height of the cylinder = r + r = 2r

Radius of the cylinder = r

CSA of the cylinder $=2\pi rh=2\pi r\left(2r\right)$

$=4\pi r^2$