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Question
The inner diameter of a circular well is 3.5 m. It is 10 m deep. Find
(i) Its inner curved surface area,
(ii) The cost of plastering this curved surface at the rate of Rs 40 per m2.
`["Assume "pi=22/7]`
Solution
Inner radius (r) of circular well = (3.5/2)m = 1.75m
Depth (h) of circular well = 10 m
Inner curved surface area = 2πrh
`=(2xx22/7xx1.75xx10)m^2`
= (44 × 0.25 × 10) m2
= 110 m2
Therefore, the inner curved surface area of the circular well is 110 m2.
Cost of plastering 1 m2 area = Rs 40
Cost of plastering 110 m2 area = Rs (110 × 40)
= Rs 4400
Therefore, the cost of plastering the CSA of this well is Rs 4400.
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