Question

Question 5
The total surface area of a cone whose radius is $\frac{r}{2}$and slant height 2l is:

A) $2\pi r(l+r)$
B) $\pi r(l+\frac{r}{4})$
C) $\pi r(l+r)$
D) $2\pi rl$​​​​​​​

Answer 1

The answer is B.
Given, radius, $R=\frac{r}{2}$ and slant height, $L=2l$

$\therefore$ Total surface area of a cone $=\pi r(L+R)=\pi \times \frac{r}{2}(2l+\frac{r}{2})=\pi r(l+\frac{r}{4})$