Question

The volume of a $1$-metre iron rod is $1386$ cu. cm. Find its diameter.

Answer 1

Volume of rod $=1386$ cu cm and height $=1$ m or $100$ cm

Volume of rod (iron rod is in the shape of cylinder) $=\pi r^{2}h$

$\Rightarrow 1386=\frac{22}{7}\times r^2\times 100$

$\Rightarrow r^2=\frac{1386\times 7}{2200}=4.41$

$\Rightarrow r=\sqrt{4.41}=2.1$cm

Diameter$=2r=2\times 2.1=4.2$cm