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Last updated at May 29, 2018 by Teachoo
Transcript
Ex13.6 ,7 A lead pencil consists of a cylinder of wood with a solid cylinder of graphite filled in the interior. The diameter of the pencil is 7 mm and the diameter of the graphite is 1 mm. If the length of the pencil is 14 cm, find the volume of the wood and that of the graphite. Volume of graphite Graphite is in shape of cylinder with Radius of graphite = r = (๐ท๐๐๐๐๐ก๐๐ ๐๐ ๐๐๐๐โ๐๐ก๐)/2 = 1/2 ๐๐ = 1/2 ร 1/10 cm = 1/20 cm Height of graphite = h = 14 cm Volume of the graphite cylinder = ฯr2h = (22/7ร1/20ร1/20ร140) mm3 = (22ร1/1ร1/20ร20) mm3 = 0.11 cm3 Volume of wood Volume of wood = Volume of pencil โ Volume of graphite Calculating Volume of the pencil Radius of pencil = r = (๐ท๐๐๐๐๐ก๐๐ ๐๐ ๐๐๐๐๐๐)/2 = 7/2 ๐๐ = 7/2 ร 1/10 cm = 7/20 cm Height of pencil = h = 14 cm Volume of the pencil = ฯr2h = (22/7ร7/20ร7/20ร140) mm3 = 5.39 cm3 Volume of wood = Volume of pencil โ Volume of graphite = 5.39 โ 0.11 cm3 = 5. 28 cm3
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