Question

The area of the base of a right circular cone is $28.26sq.m$. If its height be $4m$, find its curved surface (Take $\pi =3.14$).

• A. $47.1m^2$
• B. $42m^2$
• C. $48.8m^2$
• D. None of these

Answer 1

The correct option is A $47.1m^2$

Given, Area of base $=28.26m^2$.

$\Rightarrow \pi r^2=28.26$

$\Rightarrow r^2=\frac{28.26}{3.14}=9$

$\Rightarrow r=\sqrt{9}=3m$.

Also, height of cone $=4m$.

Now, slant height $l=\sqrt{r^2+h^2}$

$=\sqrt{3^2+4^2}=\sqrt{25}=5m$.

Therefore, curved surface area of cone $=\pi rl=3.14\times 3\times 5=47.10m^2$.

Hence, option $A$ is correct.