FYI - all standardized tests have standard deviations, and the standard deviation on the GMAT is about 30 points. So a 30 point difference on two GMATPrep tests is within the standard margin of error - it may not represent a true change in score / skill.
That's the bad news. The good news is: at least the change went in the right direction. :)
Next, did you take the test under 100% official conditions, including the essays and the number and duration of breaks? If you did, that's great - then your results are more valid. If you did not, please tell me how you deviated from official conditions - it's possible that your practice scores could be inflated, depending upon how you deviated.
I feel like I'm terrible at math and logic and that I should just give up on business school since my quantitative skills are way too low.
Don't think that way! The vast majority of people can handle it if they put in the work - it's just going to take some time (and hard work!)
In terms of what to do now... you might make it in a couple of weeks and you might not. That's a tight timeframe. You can decide to go for it, and then take the test again at a later date if you don't hit the score you want, or you can decide to postpone for now and solidify your skills a bit more before taking it.
I can give you some high level advice on the quant, but in order to give you any detailed (and therefore very helpful) advice, I need a lot of data from you first. Your overall score doesn't give me any information about your strengths and weaknesses.
If you take a ManhattanGMAT practice test, you can use this article to analyze your results; then, share your results here:
http://www.manhattangmat.com/articles/e ... -part1.cfm(The problem with GMATPrep is that it provides no data with which to analyze your performance.)
While we wait for specific data on strengths and weaknesses, I'll share with you some strategies for your actual study, whatever you're studying.
Analyzing a problem after trying it is where 80% of your learning occurs. Use this article to help:
http://www.manhattangmat.com/articles/a ... roblem.cfmThese two articles follow the above article, with two quant problems as examples:
http://www.manhattangmat.com/articles/a ... roblem.cfmhttp://www.manhattangmat.com/articles/a ... roblem.cfmIt's also important to be able to learn from your errors:
http://www.manhattangmat.com/articles/error-log.cfmAnd it's important to know how to make educated guesses:
http://www.beatthegmat.com/mba/2010/07/ ... s-on-quantIf you're having timing problems, this article can help:
http://www.beatthegmat.com/mba/2009/12/ ... management