GMAT Strategy

hi my gmat is in 1wk. I been taking the Manhattan Cat exams and score around 640 on them.

I took the Gmatprep for the first time few days ago to test my math score with it, and I guessed on all the verbal part and got a total score of 600.

I took the Gmatprep for the 2nd time few hours ago and I got a score of 550! My quantitative section I got 14 incorrect and the Verbal section I got 17 incorrect. How did I get a score of 550 but when I guessed and how most of the questions wrong on the first attempt and I got a 600?

By the way the first exam I got 15 incorrect in the quantitative section and 33 incorrect on the verbal.(I guessed all on the verbal part). People been telling me that the Gmat prep is real accurate, is my score really 550?

+ or -40

Since you scored 600, if your performance in the main test mirrors that of this test, your score should be between 560 and 640.

My question is how come I scored higher on my 2nd gmatprep exam in the math part (from 43 to 44), and didn't guess on the verbal (33 incorrect vs 17 incorrect) and manage to scored 50 points (First exam 600 2nd exam 550) lower compare to my first gmatprep exam.

Your scores depend on a lot of factors and GMATPrep is the closest you can get when it comes to estimation. The algorithm takes into account many more things than just the number of mistakes. Read more about it here:
https://www.crackverbal.com/?p=45

Hope this helps,

Arun