Find the cost of sinking a tubewell 280 m deep, having diameter 3 m at the rate of Rs. 3.60 per cubic metre. Find also the cost of cementing its inner curved surface at Rs. 2.50 per square metre.
Given,
Depth of tubewell = 280 m
Diameter of tubewell = 3 m
So radius = 
Volume of tubewell = πr2h = 
Curved surface area of tubewell = 2πrh = 
∴ cost of sinking at rate Rs 3.60/m3 = 3.60 ×1980 = Rs. 7128.
∴ cost of cementing at rate Rs. 2.50/m2 = 2.50×2640 = Rs. 6600.
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