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.

(1) inner curved surface area,
(ii) outer curved surface area,
(ii) total surface area.​

Answer 1

Given,

height, h = 77cm

inner diameter, d = 4cm

.°. inner radius, r = 2cm

And, outer diameter, D = 4.4 cm

.°. outer radius, R = 2.2 cm

1. Inner curved surface area

= 2πrh

= 2 × 22/7 × 2 × 77

= 2 × 22 × 2 × 11

= 968 cm²

2. Outer curved surface area

= 2πRh

= 2 × 22/7 × 22/10 × 77

= 2 × 22 × 22/10 × 11

= 1,064.8 cm²

3. Total surface area

= (Inner curved surface) + (Outer surface area) + 2(Base area)

= 968 + 1064.8 + {2(πR² - πr²)}

= 2032.8 + {2π(2.2² - 2²)}

= 2032.8 + (2 × 22/7 × 84/100)

= 2032.8 + 5.28

= 2,038.08 cm²