Question

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 8g/cu.cm, then the weight of the pipe is

A) 3.6 kg B) 3.696 kg C) 36 kg D) 36.9 kg

Answer 1

Answer:

Explanation:

In this type of question, we need to subtract external radius and internal radius to get the answer using the volume formula as the pipe is hollow. Oh! line become a bit complicated, sorry for that, lets solve it.

External radius = 4 cm

Internal radius = 3 cm [because thickness of pipe is 1 cm]

\begin{aligned}

\text{Volume of iron =}\pi r^2h\\

= \frac{22}{7}*[4^2 - 3^2]*21 cm^3\\

= \frac{22}{7}*1*21 cm^3\\

= 462 cm^3 \\

\end{aligned}

Weight of iron = 462*8 = 3696 gm

= 3.696 kg