None of these concepts show up very frequently on the test. Therefore, if you have only a limited amount of time to prepare, spend it on Plugging In, geometry, exponents and square roots, and other concepts that you are guaranteed to see. As a general rule, the more questions on a particular subject that are in this book, the more likely those questions are to show up on your test.
There are two kinds of group problems on the GRE. Both include overlapping groups. Because of this, you have to be careful so that you don’t confuse one for the other. As usual, once you recognize the type, use the appropriate set-up on your scratch paper, and organize your information, the solutions end up being a matter of simple arithmetic.
The first type of group problem you will recognize because it will include the words NEITHER and BOTH.
Example:
Of the 60 employees of company X, 22 have laptops, and 52 have desktop computers. If 12 of the employees have neither laptops nor desk tops, how many employees have both?
Once you recognize the type of problem, use the formula
Total = Group 1 + Group 2 + Neither – Both
So, 60 = 22 + 52 + 12 – x. x = 26.
The first type includes two overlapping groups and a population that might belong to one, the other, neither, or both. The second type actually involves four overlapping groups and a population that can belong to any two of the groups at one time. There is no option for NEITHER in this type of group problem.
Example:
Of the 60 employees at company X 25 use Macs and 35 use PCs. Four-fifths of the Mac users are in the graphics department and there are 40 people in the graphics department total, how many of the non-graphics employees use a PC?
To solve these problems, just get your pencil on your scratch paper and organize your information in a grid.
Sequence questions are really all about pattern recognition. You will recognize them because they will ask you specifically about a sequence of numbers, as in, “Each term in the sequence above is twice the previous term minus one. What is the value of the sixth term in the sequence?” or because they will involve a number that is too big to calculate, as in, “What is the value of the tens digit of 526 – 6 ?”
In both cases you will find the phrase, “What is the value of?” This is a sure tip-off that you can plug in the answer choices. As always, when you see this phrase, label your first column, assume choice (C) to be the correct answer, and work though the problem in bite-sized pieces making a new answer choice for every step.
It may be the case that this problem is really a simple matter of following directions. If that is the case, you will have to go through multiple steps to get to the correct answer. Make sure you work slowly, carefully, methodically, and, above all, do your work on your scratch paper.
In the second case, you will never be asked to calculate 526. The question contains the phrase, “What is the value of…,” but there is still no way to calculate a number of that size, even with the answer choices. Therefore, there must be a pattern. Begin to calculate the sequence, starting from the lowest term and working up. When the pattern emerges, figure out how often it repeats itself (Every third term? Every fourth term? Every fifth?). If the pattern repeats itself every fourth term, then the value of the ones digit on the eighth term will be the same as the one on the forth term. It will be the same, as well, on the twelfth, the sixteenth, the twentieth, the fortieth, and the forty-fourth. To find the value on the twenty-sixth term, just find the value on the twenty-fourth term and count up two.
If you see a strange symbol on the GRE, (it could be a star, a clover, a letter of the Greek alphabet) it doesn’t mean that math has changed since you left high school and they’ve rewritten all of the text books. It just means that you are seeing a rare functions question. The symbol will be attached to a variable and an equal sign. It acts like a series of instructions and tells you what to do in generic terms.
Example:
If x
y = 
for all integers x and y, then 10 6 =
As crazy as it looks, all this problem is telling you to do is plug in a 10 every time you see an x and a 6 every time you see a y in the equation, 
. Use your scratch paper, be meticulous, and follow directions. It’s not upper-level math, just basic arithmetic with weird looking symbols.
For more practice and a more in-depth look at The Princeton Review math techniques, check out our student-friendly guidebook, Cracking the GRE.