GMAT Strategy

Scorers with quant 50 are often interested what it takes to get a quant score of 51. In this thread I will post results from my experiments with GMATPrep to clarify the answer.

The experimental result is:
* You can answer wrong only 4 tough questions on GMATPrep and still get a Quant score of 51 (98th percentile).
* Answering two easy questions before question 10 and one tough question after that gave a score of 50 (92nd percentile). That is not always reproducible, depends on how easy the easy questions were. The easier they are, the more they hurt your score.
* Answering 5 questions wrong (3 average + 2 tough) gave a score of 50.

The point is that if you want a quant score of 51:
* you have to answer all easy questions correctly or you may skew the scoring algorithm into giving you too easy questions later and not be able to earn a 51 score. So you have to work on your precision on easy and intermediate questions, under time pressure. Easy questions usually happen in the begining of the test, when most people tend to make most mistakes.
* you have to learn to recognize and NOT fall in the well-known traps that GMAT sets up, usually in DS problems:
- verbal traps: a single modifier word changes the meaning of the quant question
- integer context: when a problem is IMPLYING integer-only solutions vs all real numbers, that resticts the possible solutions severely and often you end up with a single solution in DS problems which is sufficient. Some problems will say "integers" explicitly, in other problems involving number of people, of objects, of tickets, .... the integer solutions are implied because these variables cannot be non-integers or negative. A positive context is implied in geometry problems where the lengths cannot be negative.
- a system of two equations and two unknowns in which the second equation turns out to be a proportional version of the first one, basically having a single equation for two unknowns, which is insufficient
- a single equation for two variables but being able to solve for a combination of variables that is of interest in the problem, which is sufficient
- even power equations usually have more than one solutions and will be insufficient
- even power equations with additional restriction that rejects one of the solutions will be sufficient
etc.
* you have to zoom on the right answer of DS problems using the AD/BCE system, without reading the actual answers. That saves time and will prevent you from getting the right answer but marking the wrong one.
* you have to learn to do high-level problems with plugging in numbers, especially maximization/minimization problems with restrictions. There is no clear cut algebraic approach for those.

All of the above applies to GMATPrep, which we know is a very good estimator of your score on the actual exam. By induction, it should apply to the actual exam too.