A cube of wood supporting 200 g mass just floats in water. When the mass is removed, the cube rises by 1 cm, the linear dimension of cube is

Let l be the side of the cube. 
Volume of the cube outside = volume of water displaced due to mass.
Water displaced is 200 gm and its volume is 200 cm³.
$\mathrm{m}=\mathrm{A}\times \mathrm{\Delta y}\times \mathrm{\rho }; {\mathrm{l}}^2=200\Rightarrow \mathrm{l}=10\sqrt{2}$