A metal pipe is 77 cm long. The inner diameter of a cross section is 4 cm, the outer diameter being 4.4 cm. Find its

(i) Inner curved surface area,

(ii) Outer curved surface area,

(iii) Total surface area

Inner radius (r1) = = 2 cm

Outer radius (r2) = = 2.2 cm

Height = Length = 77 cm

(i) CSA of inner surface of pipe:

= 2r1h

= (2 * * 2 * 77) cm²

= 968 cm²

(ii) CSA of outer surface of pipe

= 2πr2h

= (2 * * 2.2 * 77) cm²

= (22 * 22 * 2.2) cm²

= 1064.8 cm²

(iii) TSA = Inner CSA + Outer CSA + Area of both circular ends of pipe

= 2πr1h + 2πr2h + 2π (r2² – r1²)

= [968 + 1064.8 + 2π {(2.2)² - (2)²}] cm²

= (2032.8 + 2 * * 0.84) cm²

= (2032.8 + 5.28) cm²

= 2038.08 cm²

Therefore, the total surface area of the cylindrical pipe is 2038.08 cm²