I would recommend not worrying about timing until you really understand the concepts. Once you know the concepts then you will better understand how to approach questions. Over time, I started to see questions, recognize the exact concept that was being tested, and then know better how to approach the question. That is the first and best way to improve speed. BUt concentrate on accuracy before you concentrate on speed.
Once you feel better about that then really concentrate on take full length or mini timed practice tests. You can do this with a question bank from kaplan, or the
GMATclub tests from this website, or any other questions you have. You can do them in groups of 10-15-20-37 questions. But just put 2 minutes on the clock for each question. Make sure to stay on track and NEVER spend more than 3 minutes on any one question. It is better to make an educated guess on a question in the middle of the test then to miss out on question you may have gotten right at the end of the test. Plus, if you leave any questions unanswered you get severly penalized. This will help keep you on track.
There is only one reason why a question will ever take over 3 minutes, and that is b/c you didn't approach it right, b/c EVERY question is designed to be solved in under 2-3 minutes MAX. So the better you understand the concepts, the better your timing will become.
Good luck!
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