gmatbusters wrote:
If x = 2y, what is the value of xy ?
(1) x > Y
(2) 3x - 2y = 14
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Since we have 2 variables (x and y) and 1 equation, D is most likely to be the answer. So, we should consider each condition on its own first.
Condition 1)
If x = 2, y = 1, then we have xy = 2.
If x = 4, y = 2, then we have xy = 8.
Since condition 1) does not yield a unique solution, it is not sufficient
Condition 2)
We have 3x - 2y = 3x - x = 2x = 14 or x = 4, y = 2 since x = 2y.
Since condition 2) yields a unique solution, it is sufficient
Therefore, B is the answer.
If the original condition includes “1 variable”, or “2 variables and 1 equation”, or “3 variables and 2 equations” etc., one more equation is required to answer the question. If each of conditions 1) and 2) provide an additional equation, there is a 59% chance that D is the answer, a 38% chance that A or B is the answer, and a 3% chance that the answer is C or E. Thus, answer D (conditions 1) and 2), when applied separately, are sufficient to answer the question) is most likely, but there may be cases where the answer is A,B,C or E.