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CBSE Class 9 Answered

Find the cost of plastering the inner surface of a circular well at the rate of Rs 30 per m2, if the inner diameter of a circular well is 2.8 m and its depth is 14 m.
Asked by Topperlearning User | 12 Oct, 2017, 08:54: AM
answered-by-expert Expert Answer

 Inner diameter of the well = 2.8 m ⇒ inner radius (r) = 1.4 m

Depth of the well (h) = 14 m

Let S denote the inner surface of the circular well which is the sum of curved surface of the well 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 space open parentheses 2 straight h space plus space straight r close parentheses straight S space equals space 22 over 7 cross times 1.4 space open parentheses 28 space plus space 1.4 close parentheses straight S space equals space 129.36 space straight m squared end style

 Cost of plastering 1 m2 = Rs 30

Cost of plastering 129.36 m2= Rs (30× 129.36) = Rs 3880.80

Answered by | 12 Oct, 2017, 10:54: AM

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