Question

In a cylinder, if radius is doubled and height is halved, curved surface area will be

(a) halved (b) doubled

(c) same (d) foru times

Answer 1

The correct option is

Let radius of the first cylinder $\left(r_1\right)$ = r

and height $\left(h_1\right)$ = h

$\therefore$ Surface area = $2\pi$ rh

If radius is doubled and height is halved

then radius $\left(r_2\right)$ = 2r and height $\left(h_2\right)=\frac{h}{2}$

Then surface area = $2\pi \left(2r\right)\times \frac{h}{2}$

=$2\pi \times 2r\times \frac{h}{2}=2\pi rh$

$\therefore$ Their surface area remains the same