The only reason for slow speed is not being confident about what we are doing on the test. we want to double check or triple check in the first 15 mins, when its obvious that the first 15 questions will give you a headstart, its not the end of the test . We are all nervous and anxious to get on with it and finish the 4 hours.
We may not realise that GMAT Math and regular Math are two different worlds and thats where the GMAT often wins. GMAT math is not hard, its just about keeping your cool, learning the concepts very very well and applying them on test day. Dont go taking computer tests unless you have studied your errors , worked on them and implemented a strategy to avoid them in the future. Master the OG, every single problem of it and study your errors. Just doing this will give you a great foundation from where you will have learnt the ETS way by practising with their problems. After that, you can try participating on the forum or try taking the practise tests with Kaplan
. Take the powerprep very close to the test date. Most of the problems in the powerprep are in the OG, but since you are taking the Powerprep close to your test date, the problems might not be as new to you. Again, dont ever rely on the practise test scores ... only take practise tests to get used to timing, the 4 hour mental torture and to build your confidence.
As obvious as it is, the only way to improve speed is to practise with a clock. Try to solve Q's under 1.5 mins to simulate the stress you will be in on test day. Yep, not fun, but i am sure after 100 problems, you will see errors you never realised you were doing and you will be more comfortable about solving problems at speed.
you should consider participating in our challenges and trying to finish as fast as possible. We had a ranking system based on time because we want you guys to work faster and faster everytime you take a challenge. this will definitely help on Test day.
If you think my advice works for you, start working on the OG and study all your errors. after you are done, come back and tell us how you are doing. If you need help at that time, we will be glad to help you with any issues you might have.
hope this helps you