phatturc, I don't think it is worth spending 5 minutes on a single question. If you REALLY see how to go about a problem or just need all that time because the question is calculation intensive, well then yes, spend 5 minutes on it. I know some people who got 770 on their GMAT and spent 10 min. on a single question. If you are fast, you can afford it. Otherwise, guess and move on. My rule of thumb is if you spend more than 3.5 minutes on a question, you better consider the option of moving on. I probably guessed on 2, at most 3, questions in my math section and still ended up with a Q49(90%). However, I do not think that I had to guess in any of the first 10. I remember that combination committee question which might have confused quite a few test takers unprepared to that kind of question but if you had to right amount of practice, you should not really need to guess in the first 10. I think the toughest questions hit you sometimes in the 15 to 25th question. Just my theory.