Q1 of 67 Page 193

The height of a cone is 28 cm and radius of its base is 21 cm. Find its curved surface area, total surface area and its volume.

Height = h = 28 cm


Radius of base = r = 21 cm


Curved surface area of cone = πrl


Where l =


⇒ l =


⇒ l =


⇒ l =


⇒ l = 35 cm


Therefore,


Curved surface area = × 21 × 35


= 22 × 21 × 5


= 2310 cm2


Total surface area of cone = curved surface area + area of base


= 2310 + πr2


= 2310 + × 21 × 21


= 2310 + 22 × 3 × 21


= 2310 + 1386


= 3696 cm2


Volume of cone = πr2h


= × × 21 × 21 × 28


= 22 × 21 × 28


= 12936 cm3


Therefore, curved surface area is 2310 cm2, total surface area is 3696 cm2 and volume is 12936 cm3


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