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.