Q26 of 137 Page 19

A closed cylinder has volume 2156 cm3. What will be the radius of its base so that its total surface area is minimum?


Volume of the cylinder = 2156 cm3


Formula for volume: V = πr2h


Therefore,



We need to find the value of r for which the total surface area will be minimum. Hence we rewrite the value of h in terms of r.


Total surface area = 2πr2 + 2πrh


Therefore,



Hence,









Therefore, r = 7cm is the answer


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