Question

The slant height and base diameter of conical tomb are $25\mathrm{m}\mathrm{and}14\mathrm{m}$ respectively. Find the cost of white-washing its curved surface at the rate of $\mathrm{Rs}.210\mathrm{per}100{\mathrm{m}}^2.(\mathrm{Assume}\mathrm{\pi }=\frac{22}{7})$

Answer 1

Slant height of conical tomb, $\mathrm{l}=25\mathrm{m}$

Base radius, $\mathrm{r}=\frac{\mathrm{diameter}}{2}=\frac{14}{2}=7\mathrm{m}$

The curved surface area of conical tomb$=\mathrm{\pi rl}$

$$\begin{gathered} =\frac{22}{7}\times 7\times 25 \\ =550 \end{gathered}$$

Curved surface area of conical tomb$=550{\mathrm{m}}^2$

Cost of white-washing $100{\mathrm{m}}^2$ area$=\mathrm{Rs}210$

Cost of white-washing $550{\mathrm{m}}^2$ area $=\mathrm{Rs}\frac{(210\times 550)}{2}$

$=\mathrm{Rs}.1155$

Hence the cost of white-washing its curved surface is $=\mathrm{Rs}.1155$