Hi hourunqing,
Don’t panic over your 80-point score drop, since your first exam was an official practice exam (from GMAC, the makers of the GMAT), and your second was from
MGMAT.
Remember, when you took the official GMAC practice exam you saw questions from past GMATs as well as a particular scoring algorithm. When you took your next exam, you probably encountered a slightly different scoring algorithm and did not see any questions from past GMATs. Since it’s difficult to compare the scores from those two exams, you might consider taking another MBA.com exam. Once you complete that next exam, we will have a better estimate of your current GMAT score.
To better assist, I’d like to learn some more about your GMAT experience and MBA goals:
1) What is your study routine? For how many hours a day can you prep for your upcoming GMAT? Do you plan to use resources other than the
OG for your prep?
2) Have you taken only one MBA prep exam and one
Manhattan prep exam? What were the score breakdowns from those exams? When you took the practice tests, did you take them under realistic conditions (e.g. in a quiet environment, no extended breaks)?
3) To which schools do you plan to apply?
4) What deadlines are you targeting?
Once I have this information, I will be happy to provide some more advice.