Question

A cylindrical pipe of $2800\mathrm{m}$ length is filled with water. If it contains $3.52{\mathrm{m}}^3$ water, then the inner radius of the pipe (in $\mathrm{cm}$ ) is___

Answer 1

Answer: 2

Let $r$ and $h$ be the radius and height of the cylinder, respectively.
$\pi r^{2}h=3.52{\mathrm{m}}^3$
$\frac{22}{7}\times r^2\times 2800=3.52$
$r^2\times 400\times 22=3.52$
$r^2=\frac{0.04}{1000}=\frac{4}{10000}$
$r^2={\left(\frac{2}{100}\right)}^2\Rightarrow r=\frac{1}{50}\mathrm{m}\Rightarrow r=2\mathrm{cm}$