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

Given, 

Height (h) = 22.5, Diameter(d) = 7m and radius(r) = 3.5m

Curved surface area of a cylinder = 2 $$\pi$$ r h ..........(1)

By substituting the above values in equation (1) we get,

$$\Rightarrow$$ 2 x $$\frac{22}{7}$$ x 3.5 x 22.5

$$\Rightarrow$$ 2 x 22 x 0.5 x 22.5 = 495

Curved surface area of the well = 495 m$$^{2}$$

Now, cost of plastering its inner curved surface at 3 per sq meter = 495 x 3 = 1485 rs

Hence, option B is the correct answer.