Q8 of 79 Page 229

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.

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 = 2rh


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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