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
(i) inner curved surface area,
(ii) outer curved surface area,
(iii) total surface area.
Solution (i)
Inner diameter of cross-section
cm
Inner radius of cross-section
cm
Height of pipe
cm
Inner curved surface area of metal pipe
Solution (ii)
Outer diameter of cross-section
cm
Outer radius of cross-section
cm
Height of pipe
cm
Outer curved surface area of metal pipe
Solution (iii)
It is very important to understand in this part that we are going to add
to inner curved surface area and outer curved surface area to get total surface area. So, the question is from where did
came up?
We are going to understand this with the help of diagram. We can see that area of portion shaded in blue is also part of the pipe.
Area of upper shaded portion would be = Area of outer circle -Area of inner circle
Area of total shaded portion would be
Therefore, total surface area of pipe =Inner curved surface area of pipe + Outer curved surface area of pipe+
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