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Volume and Surface Area - General Aptitude

Q1:

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

C 36 kg

D 36.9 kg

ANS:B - 3.696 kg

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.