Question

The inner diameter of a circular well is $3.5m$. It is $10m$ deep. Find the cost of plastering this curved surface at the rate of $Rs.40$ per $m^2$.

Answer 1

Inner diameter of well $=3.5m$

Inner radius of well $\left(r\right)=\frac{3.5}{2}m$

Height of well $\left(h\right)=10m$

Therefore,

Inner curved surface area of well

$=2\pi rh=2\times \frac{22}{7}\times \frac{3.5}{2}times10=110m^2$

Now,

Cost of plastering $=Rs.40$ per square meter

Therefore,

Cost of plastering this well $=40\times 110=Rs.4400$