Okay, to start with: the test is not scored based on the percentage correct. So the first thing to do is learn more about how the test is scored. This will have CRUCIAL implications for how you prepare for and take the exam.
First, read the Scoring section of our free e-book The GMAT Uncovered Guide (it's in your student center, even if you have just a free account with us).
Then read this article:
http://www.manhattangmat.com/blog/index ... to-win-it/And finally this one:
http://www.manhattangmat.com/blog/index ... nt-part-1/There is no answer to the question of "how many" questions you need to get right to get a certain score. You'll understand that after you go through the above resources.
Next, let's talk about how to improve! Start here:
http://www.manhattangmat.com/blog/index ... an-part-1/There are many additional resources linked in that article; follow the other links. Put together a study plan for yourself and feel free to come back here to check it with us. We'll tell you where you're on the right track and where we think you should do something differently.
Next, if you'd like to get more detailed advice on what to do, we need data on your strengths and weaknesses in order to advise you. Use the below to analyze your most recent MGMAT CAT(s):
http://www.manhattangmat.com/blog/index ... ice-tests/Then come back here and tell us the results of your analysis and what you think you should do based on that analysis. We'll tell you whether we agree and advise you further. (Note: do share an analysis with us, not just the raw data. Part of getting better is developing your ability to analyze your results - figure out what they mean and what you think you should do about them!)
If you haven't taken an MGMAT CAT yet, that's fine - go study a bit based upon what you just learned about your strengths and weaknesses, and also start to follow what the Developing Your Study Plan article says. When you feel ready to take another CAT, take one of ours (you can take 1 for free). Save your other GMATPrep for later.
Then you can come back here to give us your test analysis and we'll help you figure out where to go from there.