Find the cost of plastering the inner surface of a well at Rs. 9.50 per m2, if it is 21 m deep and diamwter of its top is 6 m.
Given,
Height of cylinder = 21 m
Diameter of cylinder = 6 m
Radius of cylinder = 
So,
Curved surface area of cylinder = 
∴ Cost of plastering the inner surface at rate Rs.9.50 per m2 = 396×9.50 = Rs.3762
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