A hollow iron pipe is 21 cm long and its external diameter is 8 cm. If the thickness of the pipe is 1 cm and iron weighs 8 g/cm3, then the weight of the pipe is:
Correct Answer: 3.696 kg
Explanation:
External radius = 4 cm,
Internal radius = 3 cm.
Volume of iron
=
❨
22
x [(4)2 - (3)2] x 21
❩cm3
7
=
❨
22
x 7 x 1 x 21
❩cm3
7
= 462 cm3.
∴ Weight of iron = (462 x 8) gm = 3696 gm = 3.696 kg.
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