Question

What is the volume of iron required to make a 70 cm long rod of 2.1 cm diameter?

Answer 1

Radius of rod (r)$=\frac{\mathrm{Diameter}}{2}=\frac{2.1}{2}=1.05\mathrm{cm}$
Height (Length) of rod (h) =70 cm
Volume of iron required to make the rod = πr²h
$$\begin{gathered} =\frac{22}{7}\times 1.05\times 1.05\times 70 \\ =242.55\mathrm{cu}\mathrm{cm} \end{gathered}$$