In the problem-solving section of the quantitative (math) portion of the test, you will be given story problems and also be required to interpret graphs and charts. If you know how the test is structured, you can gain a better score. The questions that ask for a numerical value either increase or decrease as you read the list of possible choices. If you roughly estimate the size of the number you are looking for you can zero in on the most viable answer choices. Many questions allow you to "work backwards" in that hypothetically each possible answer choice is potentially the right one. You can take away some of the work by simply plugging in each possible answer into your problem and choosing the one that fits the equation. Use a pencil and scratch paper for all of your calculations. Never assume that you have it reasoned out in your head, it's always best to prove it on paper to check for mistakes. Careless errors are the number one cause of incorrect answers in GMAT problem solving.
The data sufficiency portion is going to test your quantitative reasoning abilities, such as if you have enough data to work out the answer to the question. Memorize the five answer choices because they're the same for every question in the data sufficiency section. Never carry over information from one statement to another, an easy mistake when you are stressed for time. If a question asks for a numerical value (just a number and nothing else) it is only answerable if a numbered statement yields one and only one possible answer--not a range of answers. If you can eliminate either answer choice "A" or "B" than you can also eliminate answer choice "D." If either numbered statement (1 or 2) alone suffices to answer the question, then you can eliminate answer choices "C" and "E."
The final portion of your math GMAT section is data interpretation. You will have two to four of them and be expected to read and interpret graphical data in charts, graphs and tables. These questions are given in the problem-solving format. The question will be a verbal problem that needs to be solved rather than a numerical equation. One easy mistake is using the wrong data to answer your question. Point your finger to the data you want, then put your finger directly against the computer screen and keep it there to make sure you are connecting the right data to the right question. If the question asks for an approximation, you can estimate numbers by rounding off. Don't confuse percentages with raw numbers. Be sure to read and view all information surrounding the data, and give yourself 15-30 seconds to focus and interpret what you are looking at.