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Answers
Answer:
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:
Since the lead pencil consists of a cylinder of wood with a solid cylinder of graphite filled in the interior, the height of the graphite and wood will be the same as the height of the pencil.
Volume of the wood can be calculated by subtracting volume of graphite from volume of the pencil.
Volume of a cylinder of base radius, r and height, h = πr2h
For graphite:
Diameter of the graphite = 1 mm
Radius (r) = 1 mm = 0.5/10 cm = 0.05 cm
h = 14 cm
Volume of the graphite = πr2 h
= 22/7 × 0.05 cm × 0.05 cm × 14 cm
= 0.11 cm³
For pencil:
Diameter of the pencil = 7 mm
Radius (R) = 7 / 2 mm = 3.5/10 cm = 0.35 cm
h = 14 cm
Volume of the pencil = π R2 h
= 22/7 × 0.35 cm × 0.35 cm × 14 cm
= 5.39 cm3
Volume of wood = Volume of the pencil – Volume of the graphite
= 5.39 cm3 - 0.11cm3
= 5.28 cm3
The volume of the wood is 5.28 cm3 and the volume of graphite is 0.11 cm3.
Explanation:
:-P