The GMAT Math section doesn’t test your advanced knowledge in mathematics. Rather, it tests your problem solving ability. Therefore, calculus or another advanced math topic is never covered on GMAT math. The high school math knowledge is sufficient to answer GMAT math questions. Picking up the correct answer, however, is not as easy as its knowledge base. As said, only the basic math concepts are chosen so that everyone taking GMAT is put on a fair arena. What makes the GMAT exam difficult is the way questions being asked. How often is an individual required to resolve a ‘data sufficiency’ question, either during high school days or now? Likely never! Similarly, the word problems in the GMAT Exam require a good understanding of the way the question is being asked. Needless to say, a majority of high GMAT scorers do familiarize and train themselves in understanding the format of GMAT exam and practice working within the framework of the GMAT format.

So, first of first, you must be familiar with the format of GMAT math questions. There are 2 top categories: Problem Solving and Data Efficiency. Problem solving questions are common math questions while Data efficiency is very special. Please read How To Resolve GMAT Data Sufficiency Questions if you are not familiar with it yet.

Last and most important, practice, practice and practice!!. Take the official practice tests at least twice and study every math question. If you have time, you can find some valuable free GMAT math practice tests online. Take those practice tests and try to understand each question.

1. Memorize the five answer choices before sitting in the test center; they’re the same for each and every Data Sufficiency question.
2. Do not rely on a visual assessment of a diagram accompanying a geometry question to determine angle sizes, parallel lines, etc. In addition, do not carry any information over from one question to the next. Each question in the data sufficiency section of the GMAT stands on its own. You can count on seeing at least a few questions where a wrong answer choice tries to capitalize on this common fallacy.
3. Be careful not to carry over any information from one numbered statement to another. (Making this mistake is remarkably easy, especially under time pressure and in a momentary lapse of concentration.)
4. If a question asks for a numerical value (as opposed to a quantitative expression that includes variables), the question is answerable only if a numbered statement (1 or 2) yields one and only one possible numerical answer — not a range of values.
5. If you can eliminate either answer choice (A) or (B), then you can also eliminate answer choice (D).
6. If either numbered statement (1 or 2) alone suffices to answer the question, then you can eliminate answer choices (C) and (E).
7. You can use examples to eliminate some choices. For example, you are asked, ‘If x>0 ?’ given 2 conditions. You can find a value for x meeting Condition 1 but not Condition 2. Then find another value meeting Condition 2 but not Condition 1. In this way you can eliminate at least 2 options.
8. Data Sufficiency questions are designed to test you primarily on quantitative concepts, not on your ability to manipulate numbers (that’s what Problem Solving questions are for). So if you find yourself doing a lot of pencil work, you’re probably on the wrong track.
9. Just as in Problem Solving questions, in Data Sufficiency questions cast in a real-world setting you should make reasonable real-world assumptions. Don’t split hairs by looking for subtle meanings or ambiguous language. The test-makers are not out to trick you in this way.