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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 Rs. 40 per m2.

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Inner diameter of circular well, d = 3.5 m. 

Radius, r = \(\frac{3.5}{2}\)m

Depth of the well – height, h = 10 m. 

(i) Inner surfacer area of circular well, C.S.A. = 2πrh 

C.S.A. = 2πrh

= 22 × 0.5 × 10 = 110 m2 

(ii) Cost of plastering of area 1 m2 is Rs. 40 Cost of plastering 110 m2… ? … 

= 110 × 40 

= Rs. 4400.

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