Question

The ratio of total surface area that of lateral surface area of a cylinder whose radius is $20$cm and height $60$cm, is _________.

• A. $2:1$
• B. $3:2$
• C. $4:3$
• D. $5:3$

Answer 1

Answer: (C)

$4:3$

Let the total surface area and lateral surface area are $S_1$ and $S_2$ respectively.

$S_1=2\pi r^2+2\pi rh$

and $S_2=2\pi rh$

Thus, $\frac{S_1}{S_2}=\frac{2\pi r(r+h)}{2\pi rh}=\frac{r+h}{h}=\frac{20+60}{60}=\frac{80}{60}=\frac{4}{3}$