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

Solution:

Slant height (l) of conical tomb $=25 \mathrm{~m}$

Base radius $(r)$ of tomb $=\frac{14}{2}=7 \mathrm{~m}$

CSA of conical tomb $=\pi r l$

$=\left(\frac{22}{7} \times 7 \times 25\right) \mathrm{m}^{2}$

$=550 \mathrm{~m}^{2}$

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

Cost of white-washing $550 \mathrm{~m}^{2}$ area $=\mathrm{Rs}\left(\frac{210 \times 550}{100}\right)$

$=R_{S} 1155$

Therefore, it will cost Rs 1155 while white-washing such a conical tomb.
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