# The Knewton Blog

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## Top 10 GMAT Problem Solving Tips

Posted in Test Prep on October 15, 2010 by

The Problem Solving (PS) section of the GMAT may not be as quirky as the Data Sufficiency section of the test – but that doesn’t mean you don’t need to study for it! PS questions require more “straight math” than Data Sufficiency questions; in other words, they’ll probably be more like the questions you’re used to seeing on high school and college math tests. The best way to study? Master the basic concepts from geometry, algebra, statistics, and arithmetic — then check out these 10 helpful tips!

### 1. Make sure your fundamentals are strong.

The GMAT doesn’t allow you to use a calculator—which means you need to be quick and accurate with basic calculations. Be able to multiply and divide decimals. Know common higher powers and roots. Have fractions down to a science: Knowing right away whether 3/8 is less than 5/12 will mean you have more time later to work on more complicated calculations.

### 2. Choose numbers wisely.

Even questions that don’t contain variables can still be tackled by choosing numbers wisely. For example, if a question asks you about “a multiple of 6,” it’s probably quicker to work with a particular multiple of 6 (say, 12) than the abstract “multiple of 6.” While studying, identify the kind of problems where this strategy can be applied.

### 3. Learn how to estimate.

Estimation is an important part of the PS section. Often, a question will test your ability not to compute, but rather to make reasonable approximations. For example, the fact that 11 goes into 56 a little more than 5 times means that 11/56 must be slightly less than 1/5, or 0.2.

### 4. Practice plugging in numbers for variables.

Know what problems this strategy is useful for—and how best to apply it. Remember to always choose your numbers wisely. If a problem asks you about “1/7 of n garbage trucks,” plug in a multiple of 7 for n. Try to avoid plugging in 0 or 1 in almost every case.

### 5. Be mindful of how you label your quantities.

Whenever possible, give a label to the exact quantity that you’re trying to find, rather than, say, its square root. In other words, always be sure that the solution to the problem is also the solution to the equation you’ve set up. This will help avoid careless – and all too common – “last step” errors.

### 6.When the answer choices are numbers, they’re always in order.

If you know that the correct answer must be less than the value in choice C, you can immediately eliminate choices D and E (or choices A and B, if the answers are in decreasing order). Don’t guess randomly!

### 7. Use the answer choices in conjunction with one another.

If you’re stumped but you notice that three of the choices have a factor of ab, try to figure out where that factor comes from. If you know that the right answer choice should not have a factor of ab, eliminate all those choices in one fell swoop.

### 8. Commit the exponent rules to memory

Exponent rules are frequently tested on the Problem Solving section. Make sure to know what fractional exponents and negative exponents mean like the back of your hand. Also, be ready to answer answers about quantities with absolute values less than 1 being raised to odd and even powers.

### 9. PS questions have no extra information in the prompt.

Stuck on a question? Check to be sure you’ve used every fact supplied to you. Conversely, if you’ve solved a problem without using every fact, double-check your work; you probably haven’t solved the problem correctly.

### 10. Know the difference between “must be true” and “could be true.”

Be aware of how your approach would change for these two question types. Are there certain numbers you might want to plug in for one type but not for the other? Why or why not?