Question

The total surface area of a cone of radius $\frac{r}{2}$ and length 2l, is
(a) 2$\pi r(\mathit{1}+r)$

(b) $\mathrm{\pi r}\left(1+\frac{\mathrm{r}}{4}\right)$

(c) $\mathrm{\pi }r(1+r)$

(d) 2$\mathrm{\pi }r\mathrm{l}$

Answer 1

The formula of the total surface area of a cone with base radius ‘r’ and slant height ‘l’ is given as

Total Surface Area =

Here it is given that the base radius is ‘’ and that the slant height is ‘2l’.

Substituting these values in the above equation we have

Total Surface Area =

=

Hence the correct choice is (b).