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# Gruber's Complete GRE Guide 2015 Gruber, Gary R

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let you \u201csail\u201d through the GRE.
Show me the solution to a problem, and I\u2019ll solve that
problem. Show me a Gruber strategy for solving the
problem, and I\u2019ll solve hundreds of problems.
Here\u2019s a sample of a set of guidelines presented for mak-
ing up a GRE-type question in the math area:
The test maker is to make up a hard math problem in
the regular math multiple-choice area, which involves
(A) algebra
(B) two or more equations
(C) two or more ways to solve: one way being standard
substitution, the other, faster way using the strategy
of merely adding or subtracting equations.*
Previous examples given to the test maker for reference:
1. If x 1 y 5 3, y 1 z 5 4, and z 1 x 5 5, find the value
of x 1 y 1 z.
(A) 4
(B) 5
(C) 6
(D) 7
(E) 8
Solution: Add equations and get 2x 1 2y 1 2z 5 12;
divide both sides of the equation by 2 and we get x 1 y 1
2. If 2x 1 y 5 8 and x 1 2y 5 4, find the value of x 2 y.
(A) 3
(B) 4
(C) 5
(D) 6
(E) 7
Solution: Subtract equations and get x 2 y 5 4.
3. If y 2 x 5 5 and 2y 1 z 5 11, find the value of
x 1 y 1 z.
(A) 3
(B) 6
(C) 8
(D) 16
(E) 55
Solution: Subtract equation y 2 x 5 5 from 2y 1 z 5 11.
We get 2y 2 y 1 z 2 (2x) 5 11 2 5.
So, y 1 z 1 x 5 6. (Answer B)
Here\u2019s an example from a recent GRE.
7x 1 3y 5 12
3x 1 7y 5 6
If x and y satisfy the system of equations above, what is the
value of x 2 y ?
(A)
3
2
(B) 2
3
(C) 1
(D) 4
(E) 6
Solution: Subtract equations. We get 4x 2 4y 5 6
Factor now.
4(x 2 y) 5 6
x 2 y 5
4
6
2
3=
The Inside Track on How
Gre\u2002Questions\u2002Are\u2002developed\u2002and\u2002How\u2002
They Vary from Test to Test
*Note: See Math Strategy #13 on p. 104.
GRE2015_Intro.indd 20 4/18/14 11:24 AM
iNtroduCtioN\u2002 \u2002 \u2022\u2002 \u2002 xxi
Quantitative Comparison:
Choose Choice A if Quantity A is greater than Quantity B.
Choose Choice B if Quantity A is less than Quantity B.
Choose Choice C if Quantity A is equal to Quantity B.
Choose D if a definite comparison cannot be made
(that is, if neither Choice A, B, nor C is correct).
Given: 2x 1 y 5 6
x 1 2y 5 9
Quantity A Quantity B
x 1 y 5
Solution: Add the given equations: We get 3x 1 3y 5 15.
Divide both sides of this equation by 3. We get x 1 y 5 5.
Since x 1 y 5 5, the columns are equal, and so Choice C
is correct.
Now let\u2019s look at the actual GRE examples that the test
Choose Choice A if Quantity A is greater than Quantity B.
Choose Choice B if Quantity A is less than Quantity B.
Choose Choice C if Quantity A is equal to Quantity B.
Choose D if a definite comparison cannot be made
(that is, if neither Choice A, B, nor C is correct).
Given:
n 1 p 1 v 5 50
n 1 p 2 v 5 20
Quantity A Quantity B
v 15
Solution: Just subtract the equations above.
We get n 2 n 1 p 2 p 1 v 2 (2v) 5 30.
2v 5 30. v 5 15. Quantities are equal, so Choice C is
correct.
Choose Choice A if Quantity A is greater than Quantity B.
Choose Choice B if Quantity A is less than Quantity B.
Choose Choice C if Quantity A is equal to Quantity B.
Choose D if a definite comparison cannot be made
(that is, if neither Choice A, B, nor C is correct).
Given:
s 5 a 2 b
t 5 b 2 c
u 5 c 2 a
Quantity A Quantity B
s 1 t 1 u 0
s 1 t 1 u 5 a 2 b 1 b 2 c 1 c 2 a 5 0.
So the quantities are equal and thus Choice C is correct.
GRE2015_Intro.indd 21 4/18/14 11:24 AM
xxii
What Are Critical-
Thinking Skills?
Critical-Thinking Skills are generic skills for finding the most creative and effective way of
solving a problem or evaluating a situation. The most effective way of solving a problem is to
extract some piece of information or observe something curious from the problem and then
use one or more of the specific strategies or Critical-Thinking Skills (together with basic skills
or information you already know) to get to the next step in the problem. This next step will
catapult you toward a solution with further use of the specific strategies or thinking skills.
1. EXTRACT OR OBSERVE SOMETHING CURIOUS
2. USE SPECIFIC STRATEGIES TOGETHER WITH BASIC SKILLS
These specific strategies will enable you to focus on the process rather than just be concerned
with the end result, which usually gets you into a fast, rushed, and wrong answer. The Gruber
strategies have been shown to make test takers more comfortable with problem solving and
to make the process enjoyable. The skills will last a lifetime, and you will develop a passion for
problem solving. These Critical-Thinking Skills show that conventional \u201cdrill and practice\u201d is a
waste of time unless the practice is based on these generic thinking skills.
Here\u2019s a simple example of how these Critical-Thinking Skills can be used in a math problem:
Which is greater, 7 7
1 8 8
1 6 6
1 or 8 8
1 6 6
1 7?# # # #
Long and tedious way: Multiply 7 7
1 8 8
1 6 6
1
# # and compare it with 8 8
1 6 6
1 7# # .
Error in doing the problem the \u201clong way\u201d: You don\u2019t have to calculate; you just have to
compare, so you need a strategy for comparing two quantities.
Critical-Thinking Way: 1. Observe: Each expression contains 8 8
1 and 6 6
1 .
2. Use Strategy: Since both 8 8
1 and 6 6
1 are just weighting factors,
like the same quantities on both sides of a balance scale, just
cancel them from both multiplied quantities above.
3. You are then left comparing 7 7
1 with 7, so the first quantity, 7 7
1 ,
is greater. Thus 7 7
1 8 8
1 6 6
1
# # is greater than 8 8
1 6 6
1 7# # .

GRE2015_Intro.indd 22 4/18/14 11:24 AM
iNtroduCtioN\u2002 \u2002 \u2022\u2002 \u2002 xxiii
Here\u2019s a simple example of how Critical-Thinking Skills can be used for a Verbal problem:
If you see a word such as delude in a sentence or in a reading passage, you can assume that the
word delude is negative and probably means \u201ctaking away from something\u201d or \u201cdistracting,\u201d
since the prefix de- means \u201caway from\u201d and thus has a negative connotation. Although you may
not get the exact meaning of the word (in this case, the meaning is \u201cdeceive\u201d or \u201cmislead\u201d),
you can see how the word may be used in the context of the sentence it appears in, and thus
get the flavor or feeling of the sentence, paragraph, or sentence completion. I have researched
and developed more than 50 prefixes and roots (present in this book) that can let you make
use of this context strategy.
Notice that the Critical-Thinking approach gives you a fail-safe and exact way to the solution
without superficially trying to solve the problem or merely guessing at it. This book contains
all the Critical-Thinking Strategies you need to know for the GRE test.
I have researched hundreds of GRE tests (thousands of GRE questions) and docu-
mented 42 Critical-Thinking Strategies (all found in this book), powerful strategies
that can be used to solve questions on every test. These strategies can be used for
any Quantitative or Verbal Reasoning problem.
In short, you can learn how to solve a specific problem and thus find how to answer
that specific problem, or you can learn a powerful strategy that will enable you to
Question: Without using a calculator,