The external diameter of a cylindrical shaped iron pipe is 25 cm and its length is 20 cm. If the thickness of the pipe is 1cm, find the total surface area of the pipe.
Given : External diameter of pipe = dext = 25 cm
Thickness of pipe = 1 cm
Height of the hollow cylinder = h = 20 cm
To find : Total surface area of pipe = TSA of hollow cylinder = ?
Formula : r = 
CSA of cylinder = 2
rh
Solution : External radius of pipe = rext = 
= 
= 12.5 cm
External surface area of pipe = CSAext = 2
rexth
= 2
× 12.5 × 20
= 500
cm2
Thickness of pipe = 1 cm
∴ Internal radius of pipe = rint = rext – 1 = 12.5 – 1 = 11.5 cm
Internal surface area of pipe = CSAint = 2
rinth
= 2
× 11.5 × 20
= 460
cm2
TSA of hollow cylinder = CSAext + CSAint = 500
+ 460
= 960
cm2
∴ The total surface area of the hollow cylinder is 960
cm2.
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