Question

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.

Answer 1

Depth of well (h) = 280 m Diameter = 3 m $\therefore Radius\left(r\right)=\frac{3}{2}$ m

$\therefore$ Volume of earth dugout = $\pi r^2$ h

=$\frac{22}{7}\times \frac{3}{2}\times \frac{3}{2}\times 280m^3=1980m^3$

Rate of digging the well = Rs. 3.60 per $m^3$

$\therefore$ Cost of digging = Rs. 3.60 $\times$ 1980

= Rs. 7128

Area of inner curved surface = $2\pi$ rh

=$2\times \frac{22}{7}\times \frac{3}{2}\times 280=2640m^2$

Rate of plastering = Rs. 2.50 per $m^2$

$\therefore$ Cost of plasterin g= Rs. 2.50 $\times$ 2640

=Rs. 6600