Question

The inner diameter of a circular well is $3.5m.$ It is $10m$ deep. Find :

$\left(i\right)$ inner curved surface area.

$\left(ii\right)$ the cost of plastering this curved surface at the rate of $Rs.40$ per $m^2$.

Answer 1

Inner diameter of a well $=3.5m$

$\therefore$ Inner Radius $\left(r\right)=\frac{3.5}{2}=1.75m$

and, depth (or) height, $\left(h\right)=10m$

$\left(i\right)\therefore$ Inner curved surface area of the well

$=2\pi rh=2\times \frac{22}{7}\times 1.75\times 10$

$=440\times 0.25=110m^2$

$\left(ii\right)$ Rate of plastering per $m^2$ $=Rs.40$

$\therefore$ Total cost of plastering inner curved surface area $=Rs.40\times 110=Rs.4400$