A metal pipe is 77cm 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

Length of pipe = 77 c.m.

Inner diameter = 4 c.m.

Outer diameter = 4.4c.m.

1) Inner curved surface area

radius = inner diameter / 2 => 4 c.m./2 => 2 c.m.

curved surface area = 2 / rh => 2* 22 * 77 => 2 *22* 11 =** 968 c.m. ^{2}**

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2). Outer curved surface area

radius = outer diameter / 2 => 4.4 c.m. / 2 => 2.2 c.m.

curved surface area = 2 / rh

= 2 * 22* 2.2* 77

__________________ => **1064.8 c.m. ^{2}**

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3) total surface area

Let outer radius be R and inner radius be r

surface area on the end = 2 / ( R+r )( R -r )

= 2 *22 * ( 2.2 + 2) ( 2.2 -2)

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= 2* 22* 4.2 * 0.2

________________ **= 5.28 c.m. ^{2}**

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** total surface area **= 968 c.m.^{2} + 1064.8 c.m.^{2} +5.28 c.m.^{2} = **2038.08 c.m. ^{2}**