Question

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

(a) Inner curved surface area

(b) Outer curved surface area

(c) Total surface area.

Answer 1

Given outer radius$=R=2.2cm$; Inner radius$=r=2cm$; $h=77cm$

(a) Inner CSA$=S_1=2\pi rh=2\times \frac{22}{7}\times 2cm\times 77cm=968c{m}^2$

(b) Outer CSA$=S_2=2\pi Rh=2\times \frac{22}{7}\times 2.2cm\times 77cm=1064.8c{m}^2$

(c) TSA$=S_1+S_2+$area of two bases$=S_1+S_2+2(\pi R^2-\pi r^2)$

$=968c{m}^2+1064.8c{m}^2+2\times \frac{22}{7}\left\{\right(2.2{)}^2-2^2\}$

$=\{968+1064.8+\frac{44}{7}\times 0.84\}c{m}^2$

$=(968+1064.8+5.28)c{m}^2$

TSA$=2038.08c{m}^2$