CRITICAL REASONING - Amazon S3 REASONING This unique guide illustrates how to deconstruct arguments...

CRITICAL REASONING

This unique guide illustrates how to deconstruct arguments using inno-

vative diagramming techniques designed to build speed and improve

accuracy. Understanding the underlying structures of arguments is the

key to quick reading and precise analysis.

Verbal Preparation Guideg

Critical Reasoning GMAT Preparation Guide, 2007 Edition

10-digit International Standard Book Number: 0-9790175-5-613-digit International Standard Book Number: 978-0-9790175-5-1

Copyright © 2007 MG Prep, Inc.

ALL RIGHTS RESERVED. No part of this work may be reproduced or used in any form orby any means—graphic, electronic, or mechanical, including photocopying, recording, tap-ing, Web distribution—without the prior written permission of the publisher, MG Prep Inc.

Note: GMAT, Graduate Management Admission Test, Graduate Management AdmissionCouncil, and GMAC are all registered trademarks of the Graduate Management AdmissionCouncil which neither sponsors nor is affiliated in any way with this product.

8 GUIDE INSTRUCTIONAL SERIES

g Math GMAT Preparation GuidesNumber Properties (ISBN: 978-0-9790175-0-6)

Fractions, Decimals, & Percents (ISBN: 978-0-9790175-1-3)

Equations, Inequalities, & VIC’s (ISBN: 978-0-9790175-2-0)

Word Translations (ISBN: 978-0-9790175-3-7)

Geometry (ISBN: 978-0-9790175-4-4)

Verbal GMAT Preparation GuidesCritical Reasoning (ISBN: 978-0-9790175-5-1)

Reading Comprehension (ISBN: 978-0-9790175-6-8)

Sentence Correction (ISBN: 978-0-9790175-7-5)

5

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need to know to do well on the GMAT.

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1. ARGUMENT STRUCTURE 11

In Action Problems 23Solutions 27

2. DIAGRAMMING 29

In Action Problems 41Solutions 45

3. GENERAL STRATEGY 49

4. FIND THE ASSUMPTION 57

In Action Problems 65Solutions 73Official Guide Problem Set 91

5. DRAW A CONCLUSION 93


6. STRENGTHEN THE CONCLUSION 123


7. WEAKEN THE CONCLUSION 157


8. ANALYZE ARGUMENT STRUCTURE 191


9. MINOR QUESTION TYPES 219


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ManhattanGMATPrepthe new standard

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TABLE OF CONTENTS

ARGUMENTSTRUCTURE

g CRITICAL REASONING

Chapter 1of

In This Chapter . . .

• Identify the Parts of an Argument

• Signal Words for Argument Parts

• Real Arguments: Identifying Premises and Conclusions

• Real Arguments: Not all the Same

• Conclusion in the Question

• 2 Conclusions: Internal vs. External

• 3 Common Types of Conclusions

• 2 Tips for Finding the Conclusion

g

ARGUMENT STRUCTURE STRATEGY

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Assumptions are never

stated in the argument.

Chapter 1

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ARGUMENT STRUCTURE

The Critical Reasoning section of the GMAT involves reading brief arguments (each

argument is generally one to three sentences long) and answering questions relating to

those arguments.

In order to analyze GMAT arguments, it is important to understand their basic structure:

Premises + (Assumptions) = Conclusion

In words, premises and assumptions lead to a conclusion.

PREMISES are STATED pieces of information or evidence that support the given con-

clusion.

ASSUMPTIONS are UNSTATED parts of the argument that are necessary to reach the

given conclusion. In the formula above, the word Assumptions is put in parentheses to

signal that assumptions are NEVER stated in the written argument.

The main point of the argument is the CONCLUSION, which is logically supported by

the assumptions and premises.

Think of the conclusion as the top of a building,

supported by the building itself (the premises)

and the unseen underground foundation (the

assumptions).

Premises

Conclusion

(Assumptions)


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Premises present facts

that support the conclu-

sion of the argument.

Chapter 1

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Identify the Parts of an ArgumentIn order to do well on GMAT Critical Reasoning questions, it is essential to be able to

identify quickly the parts of an argument. Consider the following argument:

Studying regularly is one factor that has been shown to improve one's

performance on the GMAT. Melissa took the GMAT and scored a 500. If

she studies several times a week, Melissa can expect to improve her score.

In analyzing an argument, you should first look for the conclusion, which is the main

point of the argument. The conclusion is often the last sentence of an argument, but not

always. Sometimes the conclusion appears as the first sentence.

Where is the CONCLUSION? The main point of this argument is the last sentence:

If she studies several times a week, Melissa can expect to improve her score.

After finding the conclusion, look for the premises that lead to the conclusion. Premises

include ALL the pieces of information in the argument (except the conclusion).

Premises provide evidence that supports, or leads to, the conclusion.

Where are the PREMISES? Since everything except the conclusion is considered a

premise, each of the first two sentences is a premise.

Premise: Studying regularly is one factor that has been shown to improve

one's performance on the GMAT.

Premise: Melissa took the GMAT and scored a 500.

Usually, all you will need to find are the conclusion and the premises. Sometimes, how-

ever, the GMAT will ask you to identify an assumption.

Where are the ASSUMPTIONS? Assumptions are unstated parts of the argument.

Therefore, you will NEVER find an assumption stated in an argument. However,

assumptions are necessary to reach the given conclusion. One assumption in this argu-

ment is that studying several times a week qualifies as studying regularly.


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The conclusion happens

last in time, but does

not necessarily appear

last in the text of the

argument.

Chapter 1

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Signal Words for Argument PartsOne way to recognize the conclusion of an argument is by looking out for certain “sig-

nal words” that often precede a conclusion.

The most common conclusion signals on the GMAT are:

Therefore So

As a result Consequently

Suggests Thus

Indicates Hence

Accordingly It follows that

Conclusions are also signaled by their strong tone, often marked by words such as

should (“This law should be enacted . . .”).

Premises can also be recognized by certain “signal words.” The most common premise

signals on the GMAT are:

Since Because

Due to Given that

As a result of As

In order to separate the conclusion from the premises, look for the last deduction made

in the argument. The deduction that takes place last (chronologically) is always the con-

clusion. (This does not necessarily mean that the conclusion will appear last in the pas-

sage.)


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The conclusion is the

main point the speaker

is trying to argue.

Therefore, the conclu-

sion should be arguableeither way.

Chapter 1

the new standard

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Real Arguments: Identifying Premises and ConclusionsThe best way to understand the structure of GMAT arguments is to practice reading a

particular argument, identifying each point as either a premise or the conclusion.

A program instituted by a state government to raise money allows home

owners to prepay their future property taxes at a small discount. The state

then forgives the prepaid property taxes in subsequent years. Homeowners

should participate in the program in order to decrease their overall proper-

ty tax burden over time.

This argument consists of three sentences:

The CONCLUSION of this argument is the last sentence, because this is the main point

of the argument. Notice its strong tone through the use of the word should.

The first two sentences are therefore PREMISES. Notice that, in this argument, the

premises are both facts.

Here is another argument:

The proposal to hire additional dogcatchers in Newtown is a mistake.

Though there is sufficient room in the budget to pay the salaries of the dog-

catchers, there are not enough resources available for the town to also pay

for the housing and care of the additional canines that the new dogcatchers

will be expected to capture.

This argument consists of two sentences:

The CONCLUSION of this argument is the first sentence, because this is the main point

of the argument. Notice its strong tone through the use of the word mistake.

The second sentence contains several PREMISES, which provide important information

meant to support the conclusion.


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Not all GMAT argu-

ments have a stated

conclusion. Sometimes

the conclusion is in the

answer choices.

Chapter 1

the new standard

*

Real Arguments: Not all the SameNot all GMAT arguments can be neatly broken down by sentence into premises and

conclusions. Some arguments have a slightly different structure. Consider the following

example:

Transportation safety data indicates that trains are safer than cars. Since

airplanes are safer than trains, it must be that buses are more dangerous

than airplanes.


The CONCLUSION of this argument is the last part of the second sentence: it must be

that buses are more dangerous than airplanes. Notice the conclusion is signaled by

the phrase it must be that.

The rest of this passage consists of PREMISES. The first sentence is a premise that

presents information relating trains to cars. The first part of the second sentence is a

premise that gives information relating airplanes to trains.

This example illustrates that a premise and a conclusion can appear together in the same

sentence.

Now consider an example that contains NO conclusion:

Certain genetic diseases are more prevalent among certain ethnic popula-

tions. For example, Tay Sachs disease, a usually fatal genetic condition

caused by the build-up of gangliocides in nerve cells, occurs more frequently

among Ashkenazi Jews than among the general population.


Both sentences present factual information; neither presents a compelling main point or

claim. Thus, this is an argument that consists of several PREMISES but no real CON-

CLUSION.

Many GMAT critical reasoning questions ask you to draw a conclusion, make an infer-

ence, or explain a situation (selected from a set of answer choices) based solely on a

passage of premises.


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ManhattanGMATPrep

If the language of the

question is specific to

the argument, look for

the conclusion there.

Chapter 1

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Conclusion in the QuestionSometimes the conclusion of a particular argument is not in the passage itself, but

instead can be found in the question that follows the passage. Consider the following

example:

Some universities are changing the structure of financial aid awards given

to students who cannot afford to pay full tuition. In the past, the largest

proportion of financial aid distributed to students was in the form of feder-

al, interest-deferred loans. Now, these institutions are awarding a higher

proportion of grants, money that students do not need to pay back.

If, on the basis of the evidence above, it is argued that the shift from loan to

grant awards gives students the freedom to choose careers in less lucrative

professions, which of the following, if true, would most seriously weaken

that argument?

Notice that the passage itself consists of three sentences, which are each PREMISES.

The first premise points out that universities are changing the structure of financial aid

awards. The second premise describes the old structure, and the third premise describes

the new one.

The CONCLUSION of this argument is given in the question: The shift from loan to

grant awards gives students the freedom to choose careers in less lucrative profes-

sions. This is the main point of the argument. (The question goes on to ask for a way

to weaken the argument.)


19ManhattanGMATPrep

Some passages have

both an internal conclu-

sion and an external

conclusion.

Chapter 1

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Two Conclusions: Internal vs. ExternalSometimes a passage contains TWO conclusions that are opposed to one another. The

first conclusion is inside the passage itself�termed the internal conclusion. The second

conclusion is found in the question. This second conclusion�termed the external con-

clusion�makes its own assessment (usually a negative assessment) of the first conclu-

sion. Take a look at the following example:

The mayor of Middletown has proposed lowering the town sales tax from 8

percent to 5 percent, claiming that the reduction will result in more revenue

for the town government. The mayor reasons that, since the new local sales

tax will be lower than that of several neighboring towns, many residents of

nearby towns will begin shopping in Middletown.

Which of the following statements, if true, provides the best evidence that

the mayor’s reasoning is flawed?

The passage focuses on the mayor’s proposal to lower the town sales tax from 8 percent

to 5 percent. The mayor's conclusion is found in the first sentence: the reduction will

result in more revenue for the town government.

The second sentence consists of premises leading up to this conclusion. One premise is

the fact that the new local sales tax will be lower than that of several neighboring

towns. Another premise is the mayor’s claim that many residents of nearby towns

will begin shopping in Middletown. Note that this claim is not considered the conclu-

sion, because it is not the mayor’s final claim. Rather, this claim leads to the mayor’s

ultimate conclusion that the tax reduction will result in more revenue for the town gov-

ernment.

When we move on to the question that follows the argument, we see that the question

makes its own assessment of the mayor’s conclusion. The question asks for evidence

that the mayor’s reasoning is flawed. This is an external conclusion�a statement that

assesses (negatively, in this case) the conclusion made by the mayor.

Thus, we have an example of a passage that has two competing conclusions. The inter-

nal conclusion, found in the argument, is the mayor’s ultimate point. The external con-

clusion, found in the question, is a claim that comments on the mayor’s conclusion.

IN ACTION

23ManhattanGMATPrep

Chapter 1

the new standard

*

ARGUMENT STRUCTURE PROBLEM SET

Problem SetNow that you have completed your study of ARGUMENT STRUCTURE, it is time to test your

skills on a variety of different passages. The passages below exhibit a representative sampling

of argument structures. For each passage, complete the following in a notebook:

(1) Find and write out the conclusion of the passage. The conclusion may be an entire

sentence or part of a sentence. Try to be as accurate as possible in locating the exact

words of the conclusion.

(2) If the passage does not include a conclusion, indicate this with the words no given

conclusion.

Note that you are not actually answering these questions! You are only identifying the conclu-

sion of each argument; this is a skill that must be mastered in order to succeed in answering

critical reasoning questions accurately. After you are done with the entire set, you may check

your work using the answers that follow.

1. The Chinese white dolphin is a territorial animal that rarely strays far from its habitat in the

Pearl River Delta. In recent years, increasing industrial and agricultural runoff to the Delta’s

waters have caused many white dolphins to perish before they reach breeding age. Unless leg-

islation is enacted to ensure there is no further decline in the Delta’s water quality, the Chinese

white dolphin will certainly go extinct.

2. A series of research studies have reported that flaxseed oil can have a beneficial effect in

reducing tumor growth in mice, particularly the kind of tumor found in human post-menopausal

breast cancer. Thus, flaxseed oil should be recommended as an addition to the diets of all post-

menopausal women.

3. Violent video games are periodically criticized by some parents' groups, psychologists, reli-

gious organizations, and politicians. A common focus of the criticism is that video games that

allow players to act out crimes, and reward players for doing so, encourage aggressive behavior.

Though some psychological studies have shown a correlation between the playing of violent

video games and aggressive behavior, the vast majority stop short of claiming behavioral causa-

tion.

4. The fossils found in the Burgess Shale, an area high in the Canadian Rockies, are especially

valuable to evolutionary science. Due to the unique geological conditions of the region, the

fossils include appendages and soft parts that are rarely preserved. By studying these remains,

scientists are offered insights into the precursors of contemporary

life forms.

5. Tea has played a significant role in Asian culture for centuries as a staple beverage, a cura-

tive, and a symbol of status. China is considered to have the earliest records of tea, dating back

to its use as a medicine during the Han Dynasty. The use of tea as a beverage drunk for pleas-

ure on social occasions dates from the Tang Dynasty.

IN ACTION ANSWER KEY

27ManhattanGMATPrep

Chapter 1

the new standard

*

ARGUMENT STRUCTURE SOLUTIONS

1. Conclusion: Third sentence: Unless legislation is enacted to ensure there is no further

decline in the Delta’s water quality, the Chinese white dolphin will surely go extinct.

2. Conclusion: Second sentence: Thus, flaxseed oil should be recommended as an addition

to the diets of all post-menopausal women.

3. No given conclusion

4. Conclusion: First sentence: The fossils found in the Burgess Shale, an area high in the

Canadian Rockies, are especially valuable to evolutionary science.


6. Conclusion: End of second sentence: Pure Springs must produce the best tasting bottled

water currently available.

7. Conclusion: Third sentence: Thus, at least concerning the liver, it can be concluded that

drinking alcohol is no more dangerous than abstaining from alcohol.

8. Conclusion: End of first sentence: more companies should provide free ballpoint pens to

their customers.


10. Conclusion: Third sentence: So, to ensure success with any weight loss program, choose

smaller tableware for your meals.

11. Conclusion: First sentence: The cutback in physical education is the primary contribut-

ing factor to North High School’s increasing failure rate on the high school graduation

examination.

12. Conclusion: End of second sentence: the clothes will surely be a hit with young active

women.


14. Conclusion: End of third sentence: all individuals should sample a minuscule portion of

each of these foods to determine whether a particular food allergy is present.

15. Conclusion: Third sentence: Eventually, if enough people adopt meditation as a daily

practice, stress will cease to be a component of the lives of many people in the Western

world.


17. Conclusion: First sentence: To increase the productivity of the country’s workforce, the

government should introduce new food guidelines that recommend a vegetarian diet.

Number Properties, 2007 EditionISBN: 978-0-9790175-0-6

Retail: $26

Fractions, Decimals, & Percents, 2007 EditionISBN: 978-0-9790175-1-3

Retail: $26

Equations, Inequalities, & VIC's, 2007 EditionISBN: 978-0-9790175-2-0

Retail: $26

Word Translations, 2007 EditionISBN: 978-0-9790175-3-7

Retail: $26

Geometry, 2007 EditionISBN: 978-0-9790175-4-4

Retail: $26

Critical Reasoning, 2007 EditionISBN: 978-0-9790175-5-1

Retail: $26Reading Comprehension, 2007 Edition

ISBN: 978-0-9790175-6-8Retail: $26

Sentence Correction, 2007 EditionISBN: 978-0-9790175-7-5

Retail: $26

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