pratk wrote:
Can someone please help me understand this. Is my approach correct?
If m is an integer, is m odd?
1. m/2 is not an even number
2. m-3 is an even number
My understanding is that each choice should not lead to a "Maybe" answer. But can it be sufficient if it leads to a "NO" or does it always have to be a "YES".
1. If we take m=10, the result is 5 which is not even. Therefore statement is sufficient in answering No m is not odd.
2. 5-3=2 which is even. Therefore statement 2 is sufficient because it also has a unique Yes answer that m is odd.
Thus the answer is D.
No, your approach is not quite right here. When you looked at Statement 1, you only picked one value for m, m=10. You will always get *some* answer to the question when you pick a value for m. Unfortunately that doesn't tell you much. If Statement 1 is sufficient, that means the answer must *always* be the same, for *every* value of m. So you can never only test one value in a DS question. Here, using Statement 1 alone, m could certainly be 10 and thus be even, but m could also be 11 and be odd. So we can get both a yes and a no answer using Statement 1, and it is not sufficient.
Statement 2 is sufficient, however, since if m - 3 is equal to an even number, then m is equal to an even number plus 3, so must be odd.
Finally, I'd add that in real GMAT questions, the two statements can never be inconsistent. If, in a yes/no DS question, each Statement is sufficient alone, they will both need to always give the same answer: either both will always give a yes answer or both will always give a no answer. If you think one statement always gives a yes answer and the other always gives a no answer, that's a certain sign that you've done something wrong.
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