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.
Solution:
Diameter of the pencil
mm
Radius of the pencil
mm = 0.35 cm
Height of the pencil
cm
Volume of pencil
(1)
Diameter of graphite
mm = 0.1 cm
Radius of graphite
cm
Volume of graphite
(2)
Subtracting (2) from (1), we get
Volume of wood = Volume of pencil – Volume of graphite
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