Question

The inner diameter of a circular well is $2.8$m. It is $10$m deep. Find its inner curved surface area. Also find the cost of plastering this curved surface at the rate of Rs.$42$ per $m^2$?

Answer 1

We know that the curved surface area of a right circular cylinder with radius $r$ and height $h$ is $CSA=2\pi rh$.

It is given that the height of the circular well is $h=10$ m and the diameter of the circular well is $2.8$ m, and therefore the radius of the well is $\frac{2.8}{2}=1.4$ m, therefore,

$CSA=2\pi rh=2\times \frac{22}{7}\times 1.4\times 10=\frac{616}{7}=88$ m${}^2$

Therefore, the inner curved surface area is $88$ m${}^2$.

Also, the cost of plastering curved surface per m${}^2$ is Rs.$42$,

Therefore, the cost of plastering $88$ m${}^2$ is:

Rs.$42\times 88$m${}^2=$ Rs.$3696$.

Hence, the inner curved surface area is $88$ m${}^2$ and the cost of plastering curved surface per m${}^2$ is Rs.$42$ is Rs.$3696$.