Question

Find the cost of sinking a tubewell 280m deep, having 3m 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.

Answer 1

Diameter of well = 3 m
$\therefore$ Radius (r) = $\frac{3}{2}m$ and depth (h) = 280 m
(i) $\therefore$ Volume of earth dug out = $\pi r^{2}h$
= $\frac{22}{7}\times \frac{3}{2}\times \frac{3}{2}\times 280m^3=1980m^3$
Rate of sinking the well = Rs. 3.60 per $m^3$
$\therefore$ Total cost od sinking = Rs. 1980 $\times$ 3.60 per $m^3$
= Rs. 7,128
(ii) Inner curved surface area = $2\pi rh$
= $2\times \frac{22}{7}\times \frac{3}{2}\times 280m^2=2640m^2$
Rate of cementing =Rs. 2.50 per $m^2$
$\therefore$ Total cost of cementing = Rs 2.50 $\times$ 2640
= Rs. 6,600