Two vessels separately contain two ideal gases $\text{A}$ and $\text{B}$ at the same temperature, the pressure of $\mathrm{A}$ being twice that of $\text{B}$. Under such conditions, the density of $\text{A}$ is found to be $\text{1.5}$ times the density of $\text{B}$. The ratio of molecular weights of $\text{A}$ and $\text{B}$ is