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/$cm^3$, then the weight of the pipe is:
3.6 kg
3.696 kg
36 kg
36.9 kg
Explanation:
External radius = 4 cm,
Internal radius = 3 cm.
Volume of iron = $(\dfrac{22}{7} \times [(4)^2 - (3)^2] \times 21) cm^3$
= $(\dfrac{22}{7} \times 7 \times 1 \times 21) cm^3 $
= 462 cm^3
ஃ Weight of iron = (462 x 8) gm = 3696 gm = 3.696 kg.
External radius = 4 cm,
Internal radius = 3 cm.
Volume of iron = $(\dfrac{22}{7} \times [(4)^2 - (3)^2] \times 21) cm^3$
= $(\dfrac{22}{7} \times 7 \times 1 \times 21) cm^3 $
= 462 cm^3
ஃ Weight of iron = (462 x 8) gm = 3696 gm = 3.696 kg.