Question

A cylindrical pillar has a radius of 21 cm and a height of 4 m. Find:

1. The curved surface area of the pillar.
2. cost of polishing 36 such cylindrical pillars at the rate of ₹12 per m².

Answer 1

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