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 , then the weight of the pipe is  Select:
A) 3.496 kg  B) 3.696 kg  C) 3.690 kg  D) 9.696 kg  E) 3.296 kg
Explanation:   External radius = 4 cm,   Internal radius = 3 cm.   Volume of iron = =   Weight of iron = (462 x 8)gm = 3696 gm = 3.696 kg   Answer: 3.696 kg) 3.696 kg
<result>B</result>
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 , then the weight of the pipe is