The density of a gas A is thrice that of a gas B at the same temperature. The molecular weight of gas B is twice that of A. What will be the ratio of the pressures acting on B and A?

d = MRT
Let density of gas B be d. ∴ density of gas A = 3d
and the molecular weight of A be M. ∴ molecular weight of B = 2M
Since, R is gas constant and T is same for both gases, so
PA = dART/MA
and PB = dBRT/MB
PB/PA = (dB/dA) × (MA/MB) = (d/3d) × (M/2M) = 1/6