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.
Radius of pencil = 3.5 mm, h = 14 cm = 140 mm
Volume of pencil = π r2h
= (22/7) X (3.5)2 X 140 = 5390 cubic mm
Radius of lead = 0.5 mm, h = 140 mm
Volume of lead = π r2 h
= (22/7) X (0.5)2 X 140 = 110 cubic mm
Hence, volume of wood = 5390 – 110 = 5280 cubic mm
