The inner radius of a circular well is 2.1 m and its depth is 21 m. Find the cost of plastering the inner surface of a circular well at the rate of Rs. 40 per m2

Asked by Topperlearning User | 12th Oct, 2017, 08:02: AM

Expert Answer:

Given: Radius of the circular well (r) = 2.1 m, depth (h) = 21 m

Let S denote the inner surface of the well which is the sum of Curved surface area and Area of the base.

 

begin mathsize 12px style straight S space equals space 2 πrh space plus space πr squared
straight S space equals space πr open parentheses 2 straight h space plus space straight r close parentheses
straight S space equals space 22 over 7 cross times 2.1 space open parentheses 42 plus 2.1 close parentheses space
straight S space equals space 291.06 space straight m squared end style

 

Cost of 1 m2 of sheet = Rs. 40

Cost of 291.06 m2 of sheet = Rs. (40 × 291.06) = Rs. 11642.40

Answered by  | 12th Oct, 2017, 10:02: AM