A hollow cylindrical pipe has inner circumference 44 dm and outer 45 dm. Find the cost of painting it from both sides at Rs2 per m². If its length is 3.5 m.

Given ; inner circumference = 2πr1 = 44

r1 = 7dm

outer circumference = 2πr2 = 45

r2 = 7.16dm

height (h) = 3.5m = 35 dm

Total area of painting pipe = inner curved surface area + outer curved surface area of cylinder

= 2π r1h + 2π r2h

= 2π h(r1 + r2)

= 22 × 14.16

= 311.52 dm²

As, cost of 1 dm² = Rs 2

So, cost of 311.52 dm² = Rs(2 × 311.52) = Rs. 623.04