Question

the inner diameter of a well is 4.2 metre and step is 10 M find the surface area of the well find the cost of plastering it in form inside @ Rs 52 per square metre

Answer 1

Given height h = 12m.

Given the diameter of the circular well d = 4.2 meter.

Then the radius of the circular well r = d/2 = 4.2/2 = 2.1m.

(1) Inner curved surface Area = 2pirh

                                                = 2 * 22/7 * (2.1) * 12

                                                = 2 * 22 * 0.3 * 12

                                                = 158.4m^2.

(2) Given that cost of plastering per m^2 = 50.

    Then the cost of plastering of 158.4m^2 area = 158.4 * 50

                                                                                 = 7920.