Find the cost of sinking a tubewell 280 m deep,

Cost of sinking a tube well $=$ Volume of the tube well $\times$ Cost of sinking a tube well per cubic metre

$=\underline{22}_{7} \times\left(1.5^{2}\right) \times(280) \mathrm{m}^{3} \times$ Rs $3.6 / \mathrm{m}^{3}=$ Rs $7128 .$

Cost of cementing $=$ Inner surface area of the tube well $\times$ Cost of cementina per square metre

$=\left(\left(2 \times \frac{22}{7} \times 1.5 \times 280\right) \mathrm{m}^{2}\right) \times$ Rs $2.5 / \mathrm{m}^{2}=$ Rs 6600