Two vessels separately contain two ideal gases A and B at the same temperature, the pressure of A being twice that of B. Under such conditions, the density of A is found to be 1.5 times the density of B. The ratio of molecular weight of A and B is : 

\(\frac{3}{4}\)

Ideal Gas Equation : PV = nRT

P = \(\frac{\rho}{M}RT\)

⇒ M ∝ \(\frac{\rho}{P}\)

\(\frac{M_1}{M_2} = \frac{3}{4}\)