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.

(i) Radius of circular well r = 3.5/2 m and depth h = 10 m
Inner curved surface area of circular well = 2πrh
= 2 × 22/7 × 3.5/2 × 10 = 22 × 0.5 × 10 = 110 m²
Hence, the inner curved surface area of circular well is 110 m².
(ii) The cost of plastering this curved surface at the rate of Rs 40 per m² = Rs 110 × 40 = Rs 4400
Hence, the cost of plastering this curved surface at the rate of 40 per m² is RS 4400.