I've taken the GMAT three times and few of my friends have taken it twice. We've figured out an interesting pattern that apply to the answers for Quant. The important part of the system is that you need to get the first two questions right in order for it to work.

The answer choices are A,B,C,D,E. Assign a number for each one. 1, 2, 3, 4, 5.

Let's say you get B for your first answer and E for your second. You have the values of 2 and 5.

Subtract the two answers and the absolute value of the number will be your answer for the 3rd question. Keep subtracting the answer choice from the previous one until you get to 0. Once you reach 0 add up the number of selections that were C or 3 and divide them by 3. This will be your next answer.

Loof Lirpa, my friend who introduced it to me, told me that most important part about this algorithm is that you shouldn't use it because his name spelled backwards tells a lot about the validity of his theory.

Pretty funny. Just to make sure nobody takes this seriously: Loof Lirpa = April Fool.
;)