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Since we have 2 variables (x and y) and 0 equations, C is most likely to be the answer. So, we should consider conditions 1) & 2) together first. After comparing the number of variables and the number of equations, we can save time by considering conditions 1) & 2) together first.
Conditions 1) & 2):
Since 3^x < 2^y and x, y are positive, we have 2^x < 3^x < 2^y or 2^x < 2^y. It follows that x < y.
Both conditions together are sufficient.
Since this question is an inequality question (one of the key question areas), CMT (Common Mistake Type) 4(A) of the VA (Variable Approach) method tells us that we should also check answers A and B.
Condition 1)
If x = 1 and y = 2, then the answer is "yes".
If x = -1 and y = -1, then the answer is "no".
Thus, condition 1) is not sufficient on its own since it does not give a unique solution.
Condition 2)
If x = 1 and y = 2, then the answer is "yes".
If x = 2 and y = 1, then the answer is "no"
Thus, condition 2) is not sufficient on its own since it does not give a unique solution.
Therefore, C is the answer.
Answer: C
Normally, in problems which require 2 equations, such as those in which the original conditions include 2 variables, or 3 variables and 1 equation, or 4 variables and 2 equations, each of conditions 1) and 2) provide an additional equation. In these problems, the two key possibilities are that C is the answer (with probability 70%), and E is the answer (with probability 25%). Thus, there is only a 5% chance that A, B or D is the answer. This occurs in common mistake types 3 and 4. Since C (both conditions together are sufficient) is the most likely answer, we save time by first checking whether conditions 1) and 2) are sufficient, when taken together. Obviously, there may be cases in which the answer is A, B, D or E, but if conditions 1) and 2) are NOT sufficient when taken together, the answer must be E.
