GRE Prep – Secrets of Quantitative Comparisons

Some of the trickiest questions in the GRE quantitative section are the quantitative comparison questions. Different than any other questions on the test these questions measure:

• your ability to reason accurately about the relative sizes of two quantities and perceive whether or not
• your ability to determine whether enough information is provided to sufficiently answer a question

These questions are formatted similarly each time. For each question you will be given two columns and asked to determine how the quantities in each column related to one another. You will be provided with the same five possible answers for each question:

1. The quantity in Column A is greater
2. The quantity in Column B is greater.
3. The two quantities are equal.
4. The relationship cannot be determined by the information given.

To successfully tackle the QC questions there are a some key tactics to keep in mind.

First, unlike other questions there are only 4 answer choices given. This makes guessing an even better strategy than in other places on the test. Even if you can eliminate only one answer choice guessing amongst the remaining 3 gives you a much higher probability of a correct answer.

As I’ve said in other articles if you don’t need to solve for an exact answer don’t!! Treating the two columns as two sides of an equation is an instructive way to help evaluate the relative values.

If there are only numbers in both columns you can automatically eliminate answer (D). In problems that only contain numbers and have no variables there has to be a singles solution. Therefore (D) is not a viable answer because the larger quantity is determinable.

Often times QC problems are just problem solving questions. Determine whether the question is basically a word problem where you need to solve for one or both of the columns.

ETS likes to test more than just your math skills, so often times you’ll see questions that rely on logic. Here are a few “tells” to look for in your QC questions.

1. The numbers provided are very difficult = you probably aren’t just supposed to plug them in.
2. Values for variables may be related even if it isn’t spelled out. For instance can a variable be rewritten the “terms” of the other variable simply by looking at the information given?
3. Is there any missing information? If you are presented with a problem that has a classic formula within it, but you are given only some of the data required for that formula your antenna should start to twitch. That missing information is likely a  good indicator that (D) may be the most appropriate answer.

Use mirroring to put both values in a relatively similar format. This doesn’t require you to solve either side, but will help you assess the relationship between the two. For instance if you are given values with two different variables try to write one side in terms of the other.

While this is by no means a comprehensive guide to approaching the GRE QC questions it should be a good start. Supplementing with a GRE prep course is always a great way to boost your score, and help clarify tricky test elements like strategies for quantitative comparison.