Question

A hollow cylindrical pipe has inner circumference 44 and 45 cm find the cost of painting it from both side at rupees 2 per metre square if length is 3.5 m

Answer 1

given inner circumference = 44cm

--> r = 44/2π

--> r = 44/2 × 7/22

--> r = 7cm

outer circumference = 45cm

--> R = 45/2 × 7/22

--> R = 22.5 × 7/22

--> R = 157.5/22cm

given the length (height) = 3.5m = 350cm

ATQ, we have to find the cost of painting it from both side. so first we have to find it's curved surface area.

curved surface area = 2πh(R + r)

= 2 × 22/7 × 350 (157.5/22 + 7)

= 44 × 50 (311.5/22)

= 2 × 50 × 311.5

= 31150cm²

therefore total cost @ of ₹2 per m^2 = 31150 * 2 = ₹62300