Question

A metal pipe is 70 centimeter long. The inner diameter of cross section is 4 cm and the outer diameter is 4.8 cm. Find
(i) inner surface area
(ii) outer surface area
(iii) total surface area​

Answer 1

Answer:

There are two surfaces, inner and outer.

Given,

Height of the cylinder, h = 77\ cm

Outer diameter = r_1 = 4.4\ cm

Inner diameter = r_2 = 4\ cm

Outer curved surface area = 2\pi r_1h

Inner curved surface area = 2\pi r_2h

Area of the circular rings on top and bottom = 2\pi(r_2^2-r_1^2)

\therefore The total surface area of the pipe = 2\pi r_1h +2\pi r_2h+ 2\pi(r_2^2-r_1^2)

\\ = [968 + 1064.8 + 2\pi {(2.2)^2 - (2)^2}]\\ \\ = (2032.8 + 2\times \frac{22}{7}\times 0.84) \\ \\ = (2032.8 + 5.28) \\ = 2038.08\ cm^2

Therefore, the total surface area of the cylindrical pipe is 2038.08\ cm^2