When should I plug in and what numbers should I choose? (GRE and GMAT)

The GRE and GMAT are testing your ability to think critically and find efficient answers to difficult questions. Sometimes, the best way to do this is to use a strategy usually reserved as a last resort on difficult exams: plugging in numbers and hoping that one works out! 

When we plug in numbers, however, we are not doing it randomly and hoping for the best. Plugging in numbers is a  essential tool in your GRE strategy arsenal, and it's important to understand when and how to use it. There are some general tips that you can use, but the best way to get used to this strategy is to do plenty of practice problems and get a 'feel' for how this works :-)

There are a few major clues that plugging in will work. This is a good strategy if the question requires creating a complex algebraic equations that will take a lot of time and steps. In quantitative comparison questions, we suggest that you employ the plugging in method when you are comparing expressions that include variables.  In the case of multiple choice questions, you should use this strategy if the answer choices involve variables. 

The numbers you should use depend on the question and what information you are given. Sometimes the numbers are provided for you in the answer bank or as part of the question. With quantitative comparison questions that ask you to compare expressions, however, there isn't always a clear choice! In this case, we recommend using "nice" numbers that are easy to plug in and reason through, like 0, 1, -1, 1/2, -1/2, 2, and 10.  Depending on the question, these are usually solid bets. 

If you're plugging in numbers from the answer bank, it's usually a good idea to start with a number in the middle. That way, if you get a result that's higher than you expected, you'll know to try lower numbers next. Similarly, if you get a result that's lower than you expected, you'll know to try higher numbers next. 

Unfortunately, though, there's no one set of numbers that are always useful to plug in to a formula. (That would be too easy! :P) For more information on these strategies, take a look at the following video lessons:

• GRE: QC Strategies Picking Numbers
• GMAT: VICS Picking Numbers

And check out these blog posts for more information on how this process might work and some example questions:

• Does Plugging In Work on GRE Quantitative Comparison?
• GMAT Plugging in Strategies: Always Start with Answer Choice C
• GMAT Practice Problems: Variables in the Answer Choices

Remember: practice makes perfect! Now that you know when and how to plug in numbers, try this strategy on some questions and try to get the knack of it. It may take a little while to become comfortable with this strategy :D

 I hope you find these resources helpful. Happy studying! :)