Question

Find the cost of sinking a tube-well 280 m deep , having a diameter 3m at the rate of Rs 15 per cubic metre. Find also the cost of cementing its inner curved sufrace at Rs 10 per square metre.

Answer 1

Volume of the well=$\pi r^{2}h=\frac{22}{7}x\frac{32}{x}\frac{32}{x}280$
...so cost of sinking a tube well= $\frac{22}{7}x\frac{32}{x}\frac{32}{x}280\times 3.60$
=Rs.7128
...now the cost of cementing its inner curved surface area=$2\pi rh\times 2.50$
= $2x\frac{22}{7}x\frac{22}{7}x\frac{32}{x}280x2.50$ =Rs.6600