A glass beaker of mass 400 g floats in water with the open end just touching the surface of water and half of the beaker filled with water. The inner volume of the beaker is 500 $c{m}^3$. What is the density of the material of the beaker?

Mass of water in the beaker = 250 $\times 1 = 250 \mathrm{g}$

Mass of beaker + Mass of water  = 400 + 250 = 650g

So volume of water displaced = 650 ${\mathrm{cm}}^3$

As the inner volume = 500 ${\mathrm{cm}}^3$

So volume of the material of beaker = 650 - 500 = 150 ${\mathrm{cm}}^3$

$\therefore \mathrm{Density} = \frac{400}{150} = 2.67 \mathrm{g}/{\mathrm{cm}}^3$