Q. 8
The external surface area of a hollow cylinder is 540 πsq.cm. Its internal diameter is 16 cm and height is 15 cm. Find the total surface area.
Answer :
Given : External surface area of hollow cylinder = CSAext = 540
cm2
Internal diameter = d = 16 cm
Height of the hollow cylinder = h = 15 cm
To find : Total surface area = TSA of hollow cylinder = ?
Formula : r = 
CSA of cylinder = 2
rh
Solution : Internal radius of cylinder = r = 
= 
= 8 cm
Internal surface area of hollow cylinder = CSAint = 2πrh
= 2π × 8 × 15
= 16π × 15 = 240π cm2
TSA of hollow cylinder = CSAext + CSAint = 540
+ 240
= 780
cm2
∴ The total surface area of the hollow cylinder is 780
cm2.
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