Question

If the curved surface of a cylinder be doubled the area of the ends, then the ratio of its height and radius is

• A. $2:3$
• B. $1:1$
• C. $2:1$
• D. $1:2$

Answer 1

The correct option is C $2:1$

As we know that

Curved area of cylinder $=2\pi rh$ where $r$ and $h$ are radius and height, respectively.

Area of the ends of cylinder $=\pi r^2+\pi r^2=2\pi r^2$

According to the question,

Area of curve $=2\times$ Area of ends

$2\pi rh=2\times 2\pi r^2$

$h=2r\Rightarrow \frac{h}{r}=2$

Hence,

$h:r=2:1$

This is the required solution.