The inner diameter of a circular well is 3.5 m. It is 10 m deep. Find the cost of plastering its inner curved surface at Rs. 4 per square metre.
Given,
Inner diameter of circular well = 3.5 m
Radius of well = 
Height of well = 10 m
So,
Curved surface area of well = 
∴ Cost of plastering its inner curved surface at rate Rs. 4 per m2 = 110 ×4 = Rs. 440
13