A cylinder is open at both ends and is made of 1.5-cm-thick metal. Its external diameter is 12 cm and height is 84 cm. What is the volume of metal used in making the cylinder? Also, find the weight of the cylinder if 1 cm ' of the metal weighs 7.5 g.
Hint. External radius = 6 cm, internal radius = 4.5 cm.
Volume of metal =
.
It is given in the question that,
Thickness of the cylinder = 1.5 cm
External diameter of the cylinder = 12cm
Hence,
Radius = 6 cm
And,
Internal radius = 4.5cm
Height = 84cm
Hence,
We have the following measurements now,
Total volume =
= 
= 9504 cm3
Inner volume of the cylinder =
= 
= 5346 cm3
Hence,
The volume of the metal = total volume – internal volume
= 9504 – 5346
= 4158 cm3
Therefore,
Weight of the iron = 4158 × 7.5
= 31.185 kg
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