Question

A lead pencil consists of a cylinder of wood with a solid cylinder of graphite filled in the interior. The diameter of a pencil is 7 mm and 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.

Answer 1

HEY MATE!!
HERE IS YOUR ANSWER!!
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Given the diameter of the graphite filled in the pencil is 1mm. therefore radius=0.5mm

height (length)of pencil is 14cm

in mm=14×10
=140mm
volume of graphite=22/7×0.5×0.5×240
=22×0.5×0.5×20
=110mm^3
diameter of the pencil=7mm,therefore radius=7/2mm
volume of the pencil =22/7×7/2×7/2×140
=11×7×70
=5390 mm^3
hence volume of the wood pencil =5390-110
=5280mm^3
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Hope it helps you!!

Answer 2

Step-by-step explanation:

Here, h = 14 cm.

Radius of the pencil (R) = 7/ 2 mm = 0.35 cm.

Radius of the graphite (r) = 1/ 2 mm = 0.05 cm.

Volume of the the graphite = π r2h

= 22/ 7 × 0.05 × 0.05 × 14 cm³ = 0.11 cm³

Volume of the the wood = π (R2 – r2)h

= 22/ 7 × [(0.35)2 – (0.05)2] × 14 cm3

= 22/ 7 × 0.4 × 0.3 × 14 cm3 = 5.28 cm³

Hence, volume of the wood = 5.28 cm³ and volume of the graphite

= 0.11 cm³