Parallel Reasoning Question Problem Set Answer Key
1. The student body at this university takes courses in a wide range of disciplines. Miriam is a student at this university, so she takes courses in a wide range of disciplines.
Which one of the following arguments exhibits
flawed reasoning most similar to that exhibited by
the argument above?
(A) The students at this school take mathematics.
Miguel is a student at this school, so he takes
mathematics.
(B) The editorial board of this law journal has
written on many legal issues. Louise is on the
editorial board, so she has written on many
legal issues.
(C) The component parts of bulldozers are heavy.
This machine is a bulldozer, so it is heavy.
(D) All older automobiles need frequent oil
changes. This car is new, so its oil need not
be changed as frequently.
(E) The individual cells of the brain are incapable
of thinking. Therefore, the brain as a whole is
incapable of thinking.
2. Commentator: Because of teacher hiring freezes, the quality of education in that country will not improve. Thus, it will surely deteriorate.
The flawed reasoning in which one of the following
is most similar to that in the commentator’s
argument?
(A) Because Raoul is a vegetarian, he will not have
the pepperoni pizza for lunch. It follows that
he will have the cheese pizza.
(B) Given that over 250 years of attempts to prove
the Goldbach conjecture have failed, it will
probably never be proved. Hence, it is more
likely to be disproved than proved.
(C) Since funding levels for social programs are
being frozen, our society will not become
more harmonious. Thus, it may become more
discordant.
(D) Since there is a storm moving in, the outside
temperature cannot rise this afternoon.
Therefore, it must fall.
(E) The starter in Mary’s car gave out weeks ago,
and so it is impossible for the car to start.
Therefore, it will not start.
3. Most people who shop for groceries no more than three times a month buy prepared frozen dinners regularly. In Hallstown most people shop for groceries no more than three times a month. Therefore, in Hallstown most people buy prepared frozen dinners regularly.
Which one of the following arguments has a flawed
pattern of reasoning most like the flawed reasoning
in the argument above?
(A) It is clear that most drivers in West Ansland are
safe drivers since there are very few driving
accidents in West Ansland and most
accidents there are not serious.
(B) It is clear that John cannot drive, since he does
not own a car and no one in his family who
does not own a car can drive.
(C) It is clear that Fernando’s friends usually drive
to school, since all of his friends can drive
and all of his friends go to school.
(D) It is clear that most people in Highland County
drive sedans, since most people who
commute to work drive sedans and most
people in Highland County commute to
work.
(E) It is clear that most of Janine’s friends are good
drivers, since she accepts rides only from
good drivers and she accepts rides from most
of her friends.
4. Bank deposits are credited on the date of the transaction only when they are made before 3 P.M. Alicia knows that the bank deposit was made before 3 P.M. So, Alicia knows that the bank deposit was credited on the date of the transaction.
Which one of the following exhibits both of the
logical flaws exhibited by the argument above?
(A) Journalists are the only ones who will be
permitted to ask questions at the press
conference. Since Marjorie is a journalist, she
will be permitted to ask questions.
(B) We know that Patrice works only on Thursday.
Today is Thursday, so it follows that Patrice
is working today.
(C) It is clear that George knows he will be
promoted to shift supervisor, because George
will be promoted to shift supervisor only if
Helen resigns, and George knows Helen will
resign.
(D) John believes that 4 is a prime number and that
4 is divisible by 2. Hence John believes that
there is a prime number divisible by 2.
(E) Pat wants to become a social worker. It is well
known that social workers are poorly paid.
Pat apparently wants to be poorly paid.
Parallel Reasoning Question Problem Set Answer Key
All answer keys in this book indicate the source of the question by giving the month and year the LSAT
was originally administered, the Logical Reasoning section number, and the question number within that
section. Each LSAT has two Logical Reasoning sections, and so the Section 1 and Section 2 designators
will refer to the first or second Logical Reasoning section in the test, not the physical section number of the
booklet.
Question #1. Parallel Flaw. December 1999 LSAT, Section 1, #6. The correct answer choice is (B)
The stimulus in this problem exhibits an error of division, where the attributes of the whole are taken to
apply to each part of the whole. In this case, the whole is the university student body, and the part is
Miriam. You must find an answer that contains a similar whole-to-part error of division.
As you attack the answers, it becomes apparent that answer choices (A) and (B) are Contenders and
answer choices (C), (D), and (E) are Losers. We will first analyze (C), (D), and (E):
Answer choice (C): Unlike the stimulus, this answer choice contains valid reasoning and is therefore
incorrect. If that fact escaped you during your analysis, this answer choice also reverses the relationship,
moving from part to whole (the stimulus moves from whole to part).
Answer choice (D): This answer contains a Mistaken Negation, not an error of division.
Answer choice (E): This answer choice contains an error of composition, where the attributes of the parts
are mistaken for the attributes of the whole. This part-to-whole error is the reverse of the error in the
stimulus.
Most students mark answer choice (A) as a definite possibility. Answer choice (B) also looks attractive, so
look more closely at both in order to decide between them.
Answer choice (A): There are several points that differentiate the argument in this answer from the
argument in the stimulus. First, the reasoning in this answer choice is valid, and that alone makes the
answer incorrect. However, most students do not realize that the argument is valid; they are too caught up
in analyzing the part-to-whole mechanics in the answer. Second, this answer has the same subject as the
stimulus, always a red flag. Third, although it is similar in some ways to the argument in the stimulus, this
answer choice focuses on a group where each member performs a single activity: the students take
mathematics. If the students take mathematics and Miguel is a student, then he too would take
mathematics. In the stimulus, the focus is on a group that collectively performs many activities—the
students at the university “take courses in a wide range of disciplines.” Obviously, as a student at the
school, Miriam does not have to take courses in different fields and she could stick to a narrow range of
disciplines.
Answer choice (B): This is the correct answer. Like the stimulus, the focus is on a group that collectively
performs many activities: the editorial board of the law journal has “written on many legal issues.” As a
member of the editorial board, Louise need not write on many legal issues. Since the error is identical to
that in the stimulus, this answer is correct.
Question #2. Parallel Flaw-CE. December 2002 LSAT, Section 2, #26. The correct answer choice
is (D)
The commentator’s argument is short and simple:
Premise: [There are] teacher hiring freezes.
Subconclusion/
Premise: The quality of education in that country will not improve.
Conclusion: Thus, it will surely deteriorate.
The argument has several notable elements:
The error in the argument occurs in the leap from subconclusion to conclusion: just because the
quality of education will not improve does not necessarily mean it will deteriorate (it could stay the
same). This mistake occurs because the author believes in the False Dilemma of two possible
outcomes (that quality of education must either rise or fall) when there are actually three possible
outcomes.
The argument also features a causal relationship in the first sentence: teacher hiring freezes are the
cause of a lack of improvement in the quality of education.
The conclusion features strong and definite language—“will surely.” An answer choice that
deviates from this level of certainty will be incorrect.
With three distinct elements to worth with, this problem should be easy to solve. The challenge is in
deciding which element to attack first. Try to match the conclusion first because it will be the easiest (and
therefore fastest) element to identify in each answer choice:
Answer choice (B) and (C) can be eliminated because they contain conclusions—“more likely”
and “may,” respectively—that are different than “will.” Answer choice (A) has the same conclusion
and remains a Contender. Be careful with answer choice (D) because the conclusion—“must”—is
similar in certainty to “will surely.” The conclusion of answer choice (E), “will not,” remains in
contention because the negative has no effect.
With only three remaining answer choices, let’s next match the False Dilemma that underlies the
conclusion:
Answer choice (A) seemingly relies on a similar assumption to that in the stimulus (that if one
outcome does not occur then it must be the opposite outcome), but answer choice (A) is different
than the stimulus because there are many different options for pizza, not just three.
Answer choice (D) is the correct answer. Each element is matched, and a False Dilemma is used
that assumes that temperatures cannot stay the same.
Answer choice (E) is incorrect because the conclusion is identical to the premise: “impossible for
the car to start” is the same as “it will not start.”
Question #3. Parallel Flaw. October 2000 LSAT, Section 1, #22. The correct answer choice is (D)
The structure of the argument is very distinct: the two premises and conclusion each contain the quantity
indicator “most.” That structure must be paralleled in the correct answer choice, and you would be wise to
immediately check the answers upon recognizing the triple “most” formation. Let us do so now:
Answer choice (A): The second line of the answer choice contains the phrase “very few.” Since this is
different than “most,” this answer is incorrect.
Answer choice (B): The answer choice contains the phrases “cannot” and “no one,” both of which are
different than “most.”
Answer choice (C): The phrase “usually” is a synonym for “most,” but the two “all” statements are
different enough to make this answer choice suspect.
Answer choice (D): This is the correct answer, and the only one with three “mosts.”
Answer choice (E): The second line contains a conditional premise (introduced by “only”). Since the
argument does not contain a similar premise, this answer is incorrect.
Amazingly, the application of this basic structural element solves the problem very quickly. The question
itself represents a perfect example of how you should attack Parallel Reasoning questions: search for the
most distinctive element, then use that element to eliminate as many answer choices as possible. You will
not always be lucky enough to eliminate all four incorrect answer choices at once, but any answer you
eliminate puts you one step closer to your goal.
For the record, the argument makes an error of division in assuming that a general proposition about “most
people” will apply to any subset of that group. In this case, “most people who shop for groceries” could be
about the entire United States, and within this group there could be town and cities such as Hallstown that
do not conform to the general truth that applies to the whole.
Question #4. Parallel Flaw-SN. June 2001 LSAT, Section 1, #21. The correct answer choice is (C)
This tricky problem is a good example of why you can never simply glance at a question stem and assume
that you know what it says. The stem in this problem specifically indicates that the correct answer must
parallel both the logical flaws in the stimulus. As you might expect, before you reach the correct answer
the makers of the test have placed answers that display only one of the flaws.
The most obvious error in the stimulus is a Mistaken Reversal (remember, “only when” introduces a
necessary condition):
CD = bank deposits credited on the day of the transaction
3 = deposit made before 3 P.M. on that day
A = Alicia knows
First premise: CD-------------> 3
Second premise and conclusion: 3A-------------> CDA
Although most students recognize the Mistaken Reversal, they make the error of quickly glancing at the
question stem, and when they see the word “exhibits” they move to the answers without realizing there is a
second flaw. Although this action is not problematic because the correct answer will contain a Mistaken
Reversal, the danger is that a student will select the first Mistaken Reversal that appears without examining
the second flaw, and indeed, about half of the test takers erroneously choose answer choice (A) or (B),
with answer choice (B) being the more popular of the two. A student considering each answer would
recognize that answer choices (A), (B), and (C) contain Mistaken Reversals and thus there must be an
additional differentiating factor.
We will dispense with answer choices (D) and (E) because they both contain the Repeat conditional form.
In order to decide between answer choices (A), (B), and (C), we must re-examine the stimulus and
discover the second error, or at least discover a factor that will allow us to choose one of the remaining
three answers. Look carefully at the stimulus: did Alicia make the deposit herself or does she just know that
the deposit was made and the transaction credited? As stated in the stimulus, she only “knows” the events
occurred, not that they actually happened for certain. This is the second error, and a quick examination of
the three remaining answers reveals that only answer choice (C) contains the same flaw of “knowing.”
Answer choice (C) is therefore correct.
Although the “double error” language appears infrequently in Parallel Reasoning questions, you can use
the knowledge that such questions exist to implement a valuable safeguard strategy: if you find an
attractive answer choice early on and you are contemplating skipping the remaining answer choices,
before you exit the problem check to make sure the question stem does not contain a twist like the one in
this problem. Doing so could save you from missing a question.
1. The student body at this university takes courses in a wide range of disciplines. Miriam is a student at this university, so she takes courses in a wide range of disciplines.
Which one of the following arguments exhibits
flawed reasoning most similar to that exhibited by
the argument above?
(A) The students at this school take mathematics.
Miguel is a student at this school, so he takes
mathematics.
(B) The editorial board of this law journal has
written on many legal issues. Louise is on the
editorial board, so she has written on many
legal issues.
(C) The component parts of bulldozers are heavy.
This machine is a bulldozer, so it is heavy.
(D) All older automobiles need frequent oil
changes. This car is new, so its oil need not
be changed as frequently.
(E) The individual cells of the brain are incapable
of thinking. Therefore, the brain as a whole is
incapable of thinking.
2. Commentator: Because of teacher hiring freezes, the quality of education in that country will not improve. Thus, it will surely deteriorate.
The flawed reasoning in which one of the following
is most similar to that in the commentator’s
argument?
(A) Because Raoul is a vegetarian, he will not have
the pepperoni pizza for lunch. It follows that
he will have the cheese pizza.
(B) Given that over 250 years of attempts to prove
the Goldbach conjecture have failed, it will
probably never be proved. Hence, it is more
likely to be disproved than proved.
(C) Since funding levels for social programs are
being frozen, our society will not become
more harmonious. Thus, it may become more
discordant.
(D) Since there is a storm moving in, the outside
temperature cannot rise this afternoon.
Therefore, it must fall.
(E) The starter in Mary’s car gave out weeks ago,
and so it is impossible for the car to start.
Therefore, it will not start.
3. Most people who shop for groceries no more than three times a month buy prepared frozen dinners regularly. In Hallstown most people shop for groceries no more than three times a month. Therefore, in Hallstown most people buy prepared frozen dinners regularly.
Which one of the following arguments has a flawed
pattern of reasoning most like the flawed reasoning
in the argument above?
(A) It is clear that most drivers in West Ansland are
safe drivers since there are very few driving
accidents in West Ansland and most
accidents there are not serious.
(B) It is clear that John cannot drive, since he does
not own a car and no one in his family who
does not own a car can drive.
(C) It is clear that Fernando’s friends usually drive
to school, since all of his friends can drive
and all of his friends go to school.
(D) It is clear that most people in Highland County
drive sedans, since most people who
commute to work drive sedans and most
people in Highland County commute to
work.
(E) It is clear that most of Janine’s friends are good
drivers, since she accepts rides only from
good drivers and she accepts rides from most
of her friends.
4. Bank deposits are credited on the date of the transaction only when they are made before 3 P.M. Alicia knows that the bank deposit was made before 3 P.M. So, Alicia knows that the bank deposit was credited on the date of the transaction.
Which one of the following exhibits both of the
logical flaws exhibited by the argument above?
(A) Journalists are the only ones who will be
permitted to ask questions at the press
conference. Since Marjorie is a journalist, she
will be permitted to ask questions.
(B) We know that Patrice works only on Thursday.
Today is Thursday, so it follows that Patrice
is working today.
(C) It is clear that George knows he will be
promoted to shift supervisor, because George
will be promoted to shift supervisor only if
Helen resigns, and George knows Helen will
resign.
(D) John believes that 4 is a prime number and that
4 is divisible by 2. Hence John believes that
there is a prime number divisible by 2.
(E) Pat wants to become a social worker. It is well
known that social workers are poorly paid.
Pat apparently wants to be poorly paid.
Parallel Reasoning Question Problem Set Answer Key
All answer keys in this book indicate the source of the question by giving the month and year the LSAT
was originally administered, the Logical Reasoning section number, and the question number within that
section. Each LSAT has two Logical Reasoning sections, and so the Section 1 and Section 2 designators
will refer to the first or second Logical Reasoning section in the test, not the physical section number of the
booklet.
Question #1. Parallel Flaw. December 1999 LSAT, Section 1, #6. The correct answer choice is (B)
The stimulus in this problem exhibits an error of division, where the attributes of the whole are taken to
apply to each part of the whole. In this case, the whole is the university student body, and the part is
Miriam. You must find an answer that contains a similar whole-to-part error of division.
As you attack the answers, it becomes apparent that answer choices (A) and (B) are Contenders and
answer choices (C), (D), and (E) are Losers. We will first analyze (C), (D), and (E):
Answer choice (C): Unlike the stimulus, this answer choice contains valid reasoning and is therefore
incorrect. If that fact escaped you during your analysis, this answer choice also reverses the relationship,
moving from part to whole (the stimulus moves from whole to part).
Answer choice (D): This answer contains a Mistaken Negation, not an error of division.
Answer choice (E): This answer choice contains an error of composition, where the attributes of the parts
are mistaken for the attributes of the whole. This part-to-whole error is the reverse of the error in the
stimulus.
Most students mark answer choice (A) as a definite possibility. Answer choice (B) also looks attractive, so
look more closely at both in order to decide between them.
Answer choice (A): There are several points that differentiate the argument in this answer from the
argument in the stimulus. First, the reasoning in this answer choice is valid, and that alone makes the
answer incorrect. However, most students do not realize that the argument is valid; they are too caught up
in analyzing the part-to-whole mechanics in the answer. Second, this answer has the same subject as the
stimulus, always a red flag. Third, although it is similar in some ways to the argument in the stimulus, this
answer choice focuses on a group where each member performs a single activity: the students take
mathematics. If the students take mathematics and Miguel is a student, then he too would take
mathematics. In the stimulus, the focus is on a group that collectively performs many activities—the
students at the university “take courses in a wide range of disciplines.” Obviously, as a student at the
school, Miriam does not have to take courses in different fields and she could stick to a narrow range of
disciplines.
Answer choice (B): This is the correct answer. Like the stimulus, the focus is on a group that collectively
performs many activities: the editorial board of the law journal has “written on many legal issues.” As a
member of the editorial board, Louise need not write on many legal issues. Since the error is identical to
that in the stimulus, this answer is correct.
Question #2. Parallel Flaw-CE. December 2002 LSAT, Section 2, #26. The correct answer choice
is (D)
The commentator’s argument is short and simple:
Premise: [There are] teacher hiring freezes.
Subconclusion/
Premise: The quality of education in that country will not improve.
Conclusion: Thus, it will surely deteriorate.
The argument has several notable elements:
The error in the argument occurs in the leap from subconclusion to conclusion: just because the
quality of education will not improve does not necessarily mean it will deteriorate (it could stay the
same). This mistake occurs because the author believes in the False Dilemma of two possible
outcomes (that quality of education must either rise or fall) when there are actually three possible
outcomes.
The argument also features a causal relationship in the first sentence: teacher hiring freezes are the
cause of a lack of improvement in the quality of education.
The conclusion features strong and definite language—“will surely.” An answer choice that
deviates from this level of certainty will be incorrect.
With three distinct elements to worth with, this problem should be easy to solve. The challenge is in
deciding which element to attack first. Try to match the conclusion first because it will be the easiest (and
therefore fastest) element to identify in each answer choice:
Answer choice (B) and (C) can be eliminated because they contain conclusions—“more likely”
and “may,” respectively—that are different than “will.” Answer choice (A) has the same conclusion
and remains a Contender. Be careful with answer choice (D) because the conclusion—“must”—is
similar in certainty to “will surely.” The conclusion of answer choice (E), “will not,” remains in
contention because the negative has no effect.
With only three remaining answer choices, let’s next match the False Dilemma that underlies the
conclusion:
Answer choice (A) seemingly relies on a similar assumption to that in the stimulus (that if one
outcome does not occur then it must be the opposite outcome), but answer choice (A) is different
than the stimulus because there are many different options for pizza, not just three.
Answer choice (D) is the correct answer. Each element is matched, and a False Dilemma is used
that assumes that temperatures cannot stay the same.
Answer choice (E) is incorrect because the conclusion is identical to the premise: “impossible for
the car to start” is the same as “it will not start.”
Question #3. Parallel Flaw. October 2000 LSAT, Section 1, #22. The correct answer choice is (D)
The structure of the argument is very distinct: the two premises and conclusion each contain the quantity
indicator “most.” That structure must be paralleled in the correct answer choice, and you would be wise to
immediately check the answers upon recognizing the triple “most” formation. Let us do so now:
Answer choice (A): The second line of the answer choice contains the phrase “very few.” Since this is
different than “most,” this answer is incorrect.
Answer choice (B): The answer choice contains the phrases “cannot” and “no one,” both of which are
different than “most.”
Answer choice (C): The phrase “usually” is a synonym for “most,” but the two “all” statements are
different enough to make this answer choice suspect.
Answer choice (D): This is the correct answer, and the only one with three “mosts.”
Answer choice (E): The second line contains a conditional premise (introduced by “only”). Since the
argument does not contain a similar premise, this answer is incorrect.
Amazingly, the application of this basic structural element solves the problem very quickly. The question
itself represents a perfect example of how you should attack Parallel Reasoning questions: search for the
most distinctive element, then use that element to eliminate as many answer choices as possible. You will
not always be lucky enough to eliminate all four incorrect answer choices at once, but any answer you
eliminate puts you one step closer to your goal.
For the record, the argument makes an error of division in assuming that a general proposition about “most
people” will apply to any subset of that group. In this case, “most people who shop for groceries” could be
about the entire United States, and within this group there could be town and cities such as Hallstown that
do not conform to the general truth that applies to the whole.
Question #4. Parallel Flaw-SN. June 2001 LSAT, Section 1, #21. The correct answer choice is (C)
This tricky problem is a good example of why you can never simply glance at a question stem and assume
that you know what it says. The stem in this problem specifically indicates that the correct answer must
parallel both the logical flaws in the stimulus. As you might expect, before you reach the correct answer
the makers of the test have placed answers that display only one of the flaws.
The most obvious error in the stimulus is a Mistaken Reversal (remember, “only when” introduces a
necessary condition):
CD = bank deposits credited on the day of the transaction
3 = deposit made before 3 P.M. on that day
A = Alicia knows
First premise: CD-------------> 3
Second premise and conclusion: 3A-------------> CDA
Although most students recognize the Mistaken Reversal, they make the error of quickly glancing at the
question stem, and when they see the word “exhibits” they move to the answers without realizing there is a
second flaw. Although this action is not problematic because the correct answer will contain a Mistaken
Reversal, the danger is that a student will select the first Mistaken Reversal that appears without examining
the second flaw, and indeed, about half of the test takers erroneously choose answer choice (A) or (B),
with answer choice (B) being the more popular of the two. A student considering each answer would
recognize that answer choices (A), (B), and (C) contain Mistaken Reversals and thus there must be an
additional differentiating factor.
We will dispense with answer choices (D) and (E) because they both contain the Repeat conditional form.
In order to decide between answer choices (A), (B), and (C), we must re-examine the stimulus and
discover the second error, or at least discover a factor that will allow us to choose one of the remaining
three answers. Look carefully at the stimulus: did Alicia make the deposit herself or does she just know that
the deposit was made and the transaction credited? As stated in the stimulus, she only “knows” the events
occurred, not that they actually happened for certain. This is the second error, and a quick examination of
the three remaining answers reveals that only answer choice (C) contains the same flaw of “knowing.”
Answer choice (C) is therefore correct.
Although the “double error” language appears infrequently in Parallel Reasoning questions, you can use
the knowledge that such questions exist to implement a valuable safeguard strategy: if you find an
attractive answer choice early on and you are contemplating skipping the remaining answer choices,
before you exit the problem check to make sure the question stem does not contain a twist like the one in
this problem. Doing so could save you from missing a question.
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