Correct Answer: Option B
External radius = 4 cm,
Internal radius = 3 cm.
Volume of iron = (22/7 x ((4)2 – (3)2) x 21 ) cm3
= (22/7 x 7 x 1 x 21) cm3
= 462 cm3
So, Weight of iron = (462 x 8) gm
= 3696 gm = 3.696 kg.
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