Question

How much iron is needed to make a rod of length 90 cm and diameter 1.4 cm?

Answer 1

Total length = 90 cm
Diameter = 1.4 cm
Radius = 0.7 cm
Total iron required = Volume of cylinder
= $\mathrm{\pi }{r}^{2}h=\frac{22}{7}\times 0.7\times 0.7\times 90=138.6$ cm³
Thus, 138.6 cm³ of iron is required.