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Question 1:
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:
A. 3.6 kg
B. 3.696 kg
Feedback External radius = 4 cm,
Internal radius = 3 cm.
Volume of iron =22/7 x [(4)^2 - (3)^2] x 21Cu.cm
=22/7x 7 x 1 x 21Cu.cm
= 462 Cu.cm
Weight of iron = (462 x 8) gm = 3696 gm = 3.696 kg
C. 36 kg
D. 36.9 kg

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