Question
The amount of concrete required to build a concrete
cylindrical pillar whose base has a perimeter 8.8 metre and curved surface area 17.6 sq. metre, is (Take π = 22/7)Solution
Concrete required to build pillar = Volume of the cylindrical pillar The curved surface area of a cylinder = 2πrh The base of a cylinder is a circle whose perimeter = 2πr The perimeter of the base of the pillar = 8.8 m ⇒ 2πr = 8.8 ⇒ r = 1.4 m Also, Curved surface area = 17.6 m ⇒ 2πrh = 17.6 ⇒ h = 17.6/2πr ⇒ h = 2 m Now, Volume of cylindrical pillar = πr2h ⇒ πr2h = (22/7)(1.4)2 × 2 ⇒ 308/25 = 12.32 m3 ∴ Concrete required to build the pillar is 12.32 m3
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