Question

A metal pipe is $77cm$ long the inner diameter of a cross-section is $4cm$ and the outer diameter is $4.8cm.$ find it's

A. Inner curved surface area
B. Outer curved surface area
C. Total surface area

Answer 1

Let $h$ be the length, $r$ be inner radius, $R$ be outer radius
Given: $h=77cm$

$r=\frac{4}{2}=2cm$

$R=\frac{4.8}{2}=2.4cm$

A) The inner curved area $=2\pi rh$

$=2\times \pi \times 2\times 77$
$=967.61c{m}^2$

B) Outer curved area $=2\pi Rh$
$=2\times \pi \times 2.4\times 77$
$=1161.13c{m}^2$

C) Total surface area = inner surface area+outer surface area+area at the ends of pipe

Area at one end of the pipe (Circular in shape)$=\pi (R^2-r^2)$

$=\pi \times ({2.4}^2-2^2)=5.529c{m}^2$

So, Total surface area $=967.61+1161.13+(2\times 5.529)=2139.79c{m}^2$