41.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
Answer:
External radius = 4 cm,
Internal radius = 3 cm.
Volume of iron =(22/7×(42)-(32)×21)cm3
= (22/7×7 ×1×21)cm3
= 462 cm3.
Weight of iron = (462 x 8) gm = 3696 gm = 3.696 kg.
