Question

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 7mm and the diameter of the graphite is 1mm. If the length of the

pencil is 14cm, find the volume of the wood and that of graphite​

Answer 1

Answer:

volume of wood = volume of pencil - volume of graphite

volume of pencil = $\pi$r^2h

r= 7mm/2 = 3.5mm

$\pi$ = 22/7

h = 14cm = 140mm

volume = 22/7 * 3.5mm * 3.5mm * 140mm

          5390mm

volume of graphite =  $\pi$r^2h

r = 1/2 = 0.5mm

$\pi$ = 22/7

h = 14 cm = 140 cm

volume = 22/7 * 0.5 *0.5 * 140

            110mm

volume of wood = 5390mm-110mm

                        5280mm