Data Sufficiency

[GMAT math practice question]

The point (p,q) lies in which quadrant of the x-y plane?

1) (p+1, q) lies in the 2nd quadrant
2) (q-1, p) lies in the 4th quadrant

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Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution.

The first step of the VA (Variable Approach) method is to modify the original condition and the question. We then recheck the question.

Condition 1) tells us that p + 1 < 0 and q > 0, which is equivalent to p < -1 < 0 and q > 0. Thus, (p, q) is in the 2nd quadrant.
Condition 1) is sufficient.

Condition 2) tells us that q - 1 > 0 and p < 0, which is equivalent to p < 0 and q > 1 > 0. Thus, (p, q) is in the 2nd quadrant.
Condition 2) is sufficient.

Therefore, D is the answer.
Answer: D

FYI, Tip 1) of the VA method states that D is most likely to be the answer if conditions 1) and 2) provide the same information.