Question

If the height of a cylinder is doubled and its radius is halved, then what is the percentage change of its new curved surface area to its original surface area.

• A. 0
• B. 10
• C. 50
• D. 100

Answer 1

The correct option is A 0

Let the original closed surface area (CSA) = $2\pi rh$
If radius is halved and the height doubled, then new CSA
$=2\pi \times \frac{r}{2}\times 2h$
$=2\pi rh$
The new CSA is the same as the orginal surface area. So, the percentage change is 0.