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# 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.. This is the Question Number 07, Exercise 17.1 of M.L Aggarwal.

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An Important Question of class 10 Based on Mensuration Chapter of M.L Aggarwal for ICSE BOARD.
A lead pencil consists of a cylinder of wood with a solid cylinder of graphite filled in the interior. The diameter of the pencil and the diameter of the graphite is given. Find the volume of the wood and that of the graphite.
This is the Question Number 20, Exercise 17.1 of M.L Aggarwal.

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1. Given length of the pencil, h = 14 cm

Diameter of the pencil = 7 mm

radius, R = 7/2 mm = 7/20 cm

Diameter of the graphite = 1 mm

Radius of graphite, r = ½ mm = 1/20cm

Volume of graphite = r2h

= (22/7)×(1/20)2×14

= 11/100

= 0.11 cm3

Hence the volume of the graphite is 0.11 cm3

Volume of the wood = (R2-r2)h

= (22/7)×[(7/20)2-(1/20)2]14

= (22/7)×[(49/400)-(1/400)]14

= (22/7)×(48/400)×14

= 11×12/25

= 5.28 cm3

Hence the volume of the wood is 5.28 cm3

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