A block of material with density $3 \mathrm{~g} / \mathrm{cc}$ is placed on a fluid of density $7 \mathrm{~g} / \mathrm{cc}$. The fraction of volume of the piece of material outside the fluid is

Density of the material, $\rho=3 \mathrm{~g} / \mathrm{cc}$ Density of the fluid, $\sigma=7 \mathrm{~g} / \mathrm{cc}$ Let the volume of the material be $V$ and $n$ portion of the volume of the block submerged in the fluid. $\therefore$ Weight of the fluid is $V \rho g$ and weight of the submerged part is $n V \sigma g$ According to the condition of equilibrium of a floating body. $$ \begin{aligned} V \rho g & =n V \sigma g \\ \Rightarrow \quad n & =\frac{\rho}{\sigma}=\frac{3}{7} \end{aligned} $$ $\therefore$ The fraction of volume of the block outside the fluid is $1-n=1-\frac{3}{7}=\frac{4}{7}=0.57$