Hi Noblescorpion, by far the most efficient way to speed up your quant solving rate is to memorize the multiplication table you knew back in elementary. This 12x12 grid helps you out on the exam more than any other single piece of advice I can give. Many questions rely on you multiplying, dividing or squaring numbers in this range, but the real trick is that this is but one aspect of the question as a whole. If you don't get sidetracked with 10-15 or more seconds trying to solve 9x12, you can save these seconds on multiple questions and come out ahead by several minutes over the entire exam.
The other huge benefit is that you don't get sidetracked while solving a question with mechanical calculations. This keeps your brain focused on the problem at hand and eliminates unnecessary rereading and even falling for some trap answers. If you're trying to solve a question for x that requires you to divide 42 by 7, if you quickly know the answer is 6, you keep the x in mind and don't start contemplating 7 or 42 or any other superfluous number.
There are other tips that can help, but if you're running out of time for 3-4 questions, this means you're running about 5-10 minutes late. The multiplication table should get you back at least this time. Incidentally, this also teaches you the perfect squares from 1 to 12. Feel free to add 13^2 (169), 14^2 (196) and 15^2 (225) to the end of that list.
Good luck and please feel free to let me know if this worked for you or if you're already fast at mental math and are looking for other tips.
Veritas Prep | GMAT Instructor
Save $100 on Veritas Prep GMAT Courses and Admissions Consulting Services
Veritas Prep Reviews