GMAT Question

Here's one where it pays to analyze the question stem a little bit before proceeding.

The question asks for the average of \(3x\) and \(6y\), two things, and so to find the average you divide that sum by 2. \((3x+6y) / 2\) can simplify to \(x+2y\). Now it becomes clear that statement 1 suffices.

It shouldn't be too difficult to see why Statement 2 is insufficient. To really nail home that it isn't, one could use examples, though that shouldn't reeeeeally be necessary. Suppose \(x\) is 4 and \(y\) is 2. That satisfies the statement, and then the average in question is 8. However, it could also be the case that, for example, \(x\) is 1 and \(y\) is 5. In this case, the average in question is 11. Whatever. (And when I say "average", i'm really just plugging into \(x+2y\)). Since we get different answers, it's insufficient.