Question

A tank with a metal cube in it was filled with water to the brim. When the cube is removed, the water level drops to $80\%$ of its height. The edge of the cube is

• A. $15$ cm
• B. $25$ cm
• C. $10$ cm
• D. $8$ cm

Answer 1

The correct option is C $10$ cm

Volume of tank$=20\times 10\times 25=5000c{m}^3$

Drop in water level$=20\%$ of volume of brim

Volume of cube $=$ Volume of water dropped in brim

$=20\%$ of $5000c{m}^3$

$=\frac{20}{100}\times 5000$

$=1000c{m}^3$

Let edge of cube be ${}^{\prime }{a}^{\prime }$ cm.

Volume of cube$=a^3$

$\Rightarrow a^3=1000$

$a=\sqrt[3]{31000}=10cm$