Question

A lead pencil consists of a cylinder of wood with a solid cylinder of grapte filled in the
interior. The diameter of the pencil is 7mm and the diameter of the grapte is 1mm. If
the length of the pencil is 14cm, find the volume of the wood. (use �� = 22/7)

Answer 1

Volume of wood used =Volume of cylindrical pencil-Volume of graphite
=pir'^2h-pir^2h
=pih(r'^2-r^2)
22/7×14(3.5^2-0.5^2)
44(12.25-0.25)
44×12
528cm^2

Answer 2

Given 
diameter of pencil  = 7 mm
radius = 7/2
diameter of graphite = 1 mm
radius = 1/2
length of pencil = 14cm
To find = volume of wood
volume of pencil = pie*r^2*h
= 22/7*7/2*7/2*14*10
= 5310 mm^2
=531 cm^2
Volume of graphite = pie*r^2*h
=22/7*1/2*1/2*14*10
=110 mm^2
=11 cm^2
volume of wood = volume of pencil - volume of graphite 
= 531-11
=520 cm^2