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 Inner curved surface area

Question

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

Answer 1

i) Height of the pipe = 77 cm

Inner diameter = 4 cm 

Inner radius = d/2 = 4/2 = 2 cm

∴ Inner C.S.A. = 2πrh

= 2 × 22/7 × 2 × 77

= 88 × 11 = 968cm²

ii) Outer diameter = 4.4 cm 

∴ Outer radius, r = d/2 = 4.4/2 = 2.2 cm

∴ Outer C.S.A. = 2πrh 

= 2 × 22/7 x 2.2 × 77

= 96.8 × 11 

= 1064.8 cm²

iii) Total surface area

= Inner C.S.A + Outer C.S.A 

= 968 + 1064.8 

= 2032.8 cm²