Two liquids ' \(A\) ' and ' \(B\) ' form an ideal solution. At 300 K, the vapour pressure of a solution containing 1 mole of ' \(A\) ' and 3 moles of ' \(B\) ' is 550 mm Hg. At the same temperature, if one more mole of ' B ' is added to the solution, the vapour pressure of solution increases to 560 mm Hg. Then the ratio of vapour pressures of \(A\) and B in their pure state is

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.