A hollow iron pipe is 21cm long and its external diameter is 8cm. If the thickness of the pipe is 1cm and iron weighs 8g/cm 3 , then the weight of pipe is : - IQ786

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A hollow iron pipe is 21cm long and its external diameter is 8cm. If the thickness of the pipe is 1cm and iron weighs 8g/cm 3 , then the weight of pipe is :

A hollow iron pipe is 21cm long and its external diameter is 8cm. If the thickness of the pipe is 1cm and iron weighs 8g/cm 3 , then the weight of pipe is :

3.696kg

6.696kg

4.696kg

None of these

Explanation

Volume of iron $= π (R^{2} - r^{2}) \times h$

$= π (4^{2} - 3^{2}) \times 21$

$= \frac{2 2}{7} \times (16 - 9) \times 21$

$= 462 c m^{2}$

Weight $= \frac{8 \times 4 6 2}{1 0 0 0} k g = 3.696 k g$