DS: What is the ratio of r to s? (1) r + s = 7 (2) r(square) - s(square) = 7 Soln: In the MGMAT the answer mentioned is C (Both are required to answer the question.) However I am not convinced. I think the answer should be B.(Choice B is sufficient). Reason: 1 4 9 16 25 The difference is 7 only when...

Soln:
A2 means A square in the solution below.
Earlier the equation looked like C = A2 / B.
Now u have replaced the B with 2B but you still want no change in the equation
so C = (1.4A)square / 2B = 1.96A2 / 2B = A2/B.

So you need to increase A by 40% for no effective change.

Hope it helps.