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:
Answer: Option B
External radius = 4 cm,
Internal radius = 3 cm.
Weight of iron = (462 x 8) gm = 3696 gm = 3.696 kg.