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	Choose the correct choice:	A) 3.6 kg	B) 3.696 kg	C) 36 kg	D) 36.9 kg	E) None of these
Explanation:   External radius = 4 cm,   Internal radius = 3 cm.   Volume of iron = [(22/7) × (42 - 32) × 21]cm3 = 462 cm3   Weight of iron = (462 x 8)gm = 3696 gm = 3.696 kg   Answer: 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 8 g/cm3 , then the weight of the pipe is