Substance A has a density of 3.0g/cm^3 and substance B has a density of 4.0g/cm^3.
In order to obtain equal masses of these two substances, the ratio of the volume of A to the volume of B will be equal to
Density of A = 3.0 g/cm^3
Density of B = 4.0 g/cm^3
Ratio of densities of A and B = 3/4 or 3:4
As density is inversely proportional to volumes for equal mass, ratio of volumes of A and B is given by ratio of inverse of densities.
Thus ratio of densities of A and B = (1/3)/(1/4) or 4:3
Option B0 of the given choices is correct.
Since the masses of the two substances are equal,
volume of A* density of A = volume of B * density of B, as the mass is the product of volume and density.
The ratio, volume of A/ Volume of B = density of B/ density of A = 4g per ccm/3 g per ccm =4/3
Volume of A : Volume of B = 4:3 for their masses to be equal.