Question

A cylindrical cistern whose diameter is $21cm$ is partly filled with water. If a rectangular block of iron $14cm$ in length, $11cm$ in breadth and $12cm$ in thickness if wholly immersed in water, by how many centimetres will the water level rise? $(\pi =\frac{22}{7})$

Answer 1

Volume of block $=14\times 11\times 12$ cu.m
Radius of the tank $=21\times \frac{1}{2}=\frac{21}{2}cm$
Volume of the cylinder $\pi r^{2}h=14\times 11\times 12$
$h=\frac{14\times 11\times 12}{\pi r^2}=\frac{14\times 11\times 12}{\frac{22}{7}\times \frac{21}{2}\times \frac{21}{2}}$
$\therefore h=5\frac{1}{3}$