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Probability

Question

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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 र 40 per m².

Solution

(i) 2r = 3.5 m

rightwards double arrow space space space space space space space straight r equals fraction numerator 3.5 over denominator 2 end fraction space straight m rightwards double arrow space space space space space space space straight r space equals space 1.75 space straight m space space space space space space space space space space straight h space equals space 10 space straight m

∴ Inner curved surface area of the circular well = 2πrh

equals 2 cross times 22 over 7 cross times 1.75 cross times 10 equals 110 space straight m squared.

(ii) Cost of plastering the curved surface at the rate of र 40 per m²= र 110 x 40 = र 4400.

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