A well has to be dug out that is to be 22.5 m deep and of diameter 7 m. Find the cost of plastering the inner curved surface at Rs. 3 per sq.meter :

Answer: Option C

Curved surface area :
$$\begin{array}{rl}& =2\pi rh\\ & =\left(2\times \frac{22}{7}\times \frac{7}{2}\times 22.5\right){\text{m}}^2\\ & =495{\text{m}}^2\end{array}$$
∴ Cost of plastering :
= Rs. (495 × 3)
= Rs. 1485