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Question
A cylindrical pillar has a radius of 21 cm and a height of 4 m. Find:
- The curved surface area of the pillar.
- cost of polishing 36 such cylindrical pillars at the rate of ₹12 per m2.
Solution
r = 21 cm, h = 4 m = 400 cm
i. C.S.A = 2πrh
= `2 xx 22/7 xx 21 xx 400`
= 52800 cm2
= `52800/(100 xx 100) = 5.28` m2
ii. Rate = ₹12/m2
Area to be polished = (5.28 × 36) m2
Cost = 12 × Area
= 12 × 5.28 × 36
= ₹2280.96
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