Question

The radius of base of a cone is $5$ cm and height of the cone is $12$ cm. Find its curved surface area.

• A. $204.3{\text{cm}}^2$(approx)
• B. $102.8{\text{cm}}^2$(approx)
• C. $40.8{\text{cm}}^2$(approx)
• D. $52{\text{cm}}^2$(approx)

Answer 1

The correct option is A $204.3{\text{cm}}^2$(approx)

The curved surface area of a cone $=\pi rl$, where $r$ is the radius and $l$ is slant height.

Given, $r=5cm$ and $h=12cm$.

We need to calculate slant height, using the formula $l^2=r^2+h^2$, where $h$ is height.

So, $l^{}=\sqrt{r^2+h^2}$ =$\sqrt{5^2+{12}^2}=13$.

We know,

curved surface area of a cone $=\pi rl$ $=\frac{22}{7}\times 5\times 13$ $=204.28c{m}^2$.

Hence, the answer is $204.28c{m}^2\approx 204.3c{m}^2$.

Therefore, option $A$ is correct.