Problem Solving is a rather ritzy name for "regular" math problems. A Problem Solving question, amazingly enough, actually expects you to solve a problem. This is different from the Quantitative Comparison questions, in which you often don't need to solve the problem through to the bitter end — you just compare the quantities.
Some of you haven't taken math classes in a long, long time. Maybe you are a senior in college, and because you tested out of your math while you were still in high school, you never took any math at all in college. Maybe you're returning to school after spending several years working or having a family or traveling or pursuing the idle and decadent lifestyle of the independently wealthy. Whatever the cause, you may be so rusty in math that your pencil creaks when you pick it up. Of course, you're not going to get every single math question correct; you should realize that you don't have to. The following suggestions help you maximize your points with a minimum of time and bother.
1. Read the problem through carefully and jot down on your scratch paper what the question is asking for.
People who are really math-phobic often miss this crucial point. It's easy to "predict" or "anticipate" what the question is asking for and not take note of what it really wants. Your goal is to give 'em what they want. If the question asks for a circumference, circle or jot down the word circumference and don't solve for an area. If the question wants you to find the number of hours already worked rather than the total number of hours a job would take, be sure that you supply the correct figure.
Of course, of course, of course, the answer choices feature trap answers; this goes without saying on the GRE. If the question asks for the perimeter, you can bet your bottom dollar that the area will also be one of the answers — it's a trap for those of who don't read the question carefully. Just because the answer you got is staring you in the face does not mean that it is the correct answer. It might be . . . or it might be a trap. Before you press the CONFIRM button on your computer, go back and look at the information: Are you answering the right question?
2. Preview the answer choices; look to see how precise your answer has to be and how careful you have to be on the decimal points.
If the answer choices are 4, 5, 6, 7, and 8, you probably have to solve the problem to the bitter end, calculating rather than estimating. This type of problem may take a long time. However, if the answer choices are .05, .5, 5, 50, and 500, you know that the digit is definitely going to be a 5 and that you have to keep your decimal point straight. You may be able to use common sense on this type of problem and estimate the answer without working it out.
3. Solve the problem forwards and backwards.
Work out the problem and get an answer; then plug that answer back into the problem to make sure that it makes sense. If you found the average of 4, 6, 7, 9, and 10 to be 36, you can look at the answer and reason that you made a mistake somewhere because the average can't be bigger than the biggest number. (Did you see the mistake? If you got 36, you found the sum of the terms but forgot to divide by the number of terms. "Interim" answers of this sort are common trap answer choices on the GRE.)