Hi zeallous,
Brent's approach (that TESTs a Value) is a great way to answer this question; it's exactly how I would have approached this prompt.
This prompt is built around an interesting Number Property, which you could have used to answer the question without doing much math at all.
We're told that Q is an ODD number, we're dealing with CONSECUTIVE INTEGERS and we're asked for the LARGEST INTEGER..
Take a look at answer B. Since Q is ODD, will answer B EVER be an integer???
The answer is NO (we'd end up with a fraction, so B can't be the answer.
This same rule holds true for answer C and E. So, we've eliminated B, C and E.
Now look at D; we're taking (Q+119) and cutting it IN HALF. That math doesn't seem like it would produce the LARGEST INTEGER that we're looking for. Eliminate D.
The answer must be A. It would certainly give us an integer: (ODD - 1)/2 = INTEGER. Add THAT integer to 120 and you either get 120 or a bigger integer.
GMAT assassins aren't born, they're made,
Rich