LSAT Discussion Forum

Complete Question Explanation

Parallel Reasoning—SN. The correct answer choice is (C)

This stimulus contains a conditional argument. It begins with a rule, that “no nonfiction book by Carriage Books has ever earned a profit.” We can diagram this rule as:

• Sufficient       Necessary
  
  Nonfiction             Profit

Next, we are told that Carriage books earned a profit on every book it published last year, which invokes the contrapositive of the rule from the first sentence, applicable to each book published last year:

     

• Profitall books             Nonfiction

The conclusion, that Carriage Books did not publish a non-fiction book last year, is the valid result of the application of the rule in the first sentence to the fact in the second sentence, as shown above in the diagram of the contrapositive.

This is a Parallel Reasoning question. Our prephrase is that the correct answer choice will contain a valid conditional relationship containing a rule, a fact that invokes the contrapositive of the rule, and a conclusion stating that the necessary condition of the contrapositive must be the case. Further, we are dealing with two categories of items associated with Carriage Books, both fiction books and non-fiction books.

Answer choice (A): There are two problems with this answer choice. First, the rule in the first sentence had to do with a major movie. However, the conclusion deals with a “movie” and not a “major movie.” More importantly, the conclusion does not reflect the necessary condition of the contrapositive. In this case, the necessary condition of the contrapositive of the rule would be that the actor is not represented by Mira Roberts.

Answer choice (B): Here, the conclusion results from a statement of the rule, not its contrapositive.

Answer choice (C): This is the correct answer choice. We can diagram this argument as:

• Rule: marketing division employee bonus
  
  and the contrapositive of the rule:
  
  bonus marketing division employee
  
  Fact: every systems analyst received a bonus (bonus)
  
  Conclusion: none of the systems analysts are marketing division employees
  (i.e., marketing division employee)

As shown by the argument breakdown above, the argument provides a rule, a fact that triggers the contrapositive of the rule, and a conclusion that is the necessary condition of the contrapositive. Also, just like the stimulus dealt with two distinct categories of book, this answer choice deals with two distinct categories of employee, marketing division employees and systems analysts , who are not marketing division employees.

Answer choice (D): This is a very attractive answer choice, because it also has a rule, a fact triggers the contrapositive of the rule, and a conclusion that is the necessary condition of the contrapositive. However, what distinguishes this answer choice from the stimulus is that it does not contain two discrete items, such as the fiction and non-fiction books, or the two distinct types of employee in answer choice (C).

Answer choice (E): Here, the answer choice is incorrect because it changes a term from the rule to the conclusion. The rules discussed Conway Flooring installing hardwood floors for customers in Woodbridge, while the conclusion references the company installing hardwood flooring generally.

I'm having trouble understanding the language in answer choice C. Maybe it's because I misidentified the initial argument we were asked to match.
I diagramed the original argument as NF(Carriage Books)---> (no) earned profit.
Followed by earned profit----> NF(no)
This looks like a valid contrapositive, so I went through the answer choices and missed answer choice C. The language in C caused me to diagram it as Pranwich Corporation----> (no) bonus in marketing division
From there I saw a new group(systems analysts) and discarded this answer choice. With my incorrect diagramming, I would have diagrammed the second part as (no) bonus to marketing division and then I got lost from there.
I see from the explanation that the correct diagram is PC marketing--->(no) Bonus
and Bonus---->(no) marketing
But I'm still confused because it says if you're in marketing you don't get a bonus, and then it says you got a bonus if you are a systems analyst which is not the same as the contrapositive, because it does not say bonus for marketing, but instead bonus for a new department, systems analyst.
I hope this makes sense. Thanks for the help.

Looks to me like you have it all right PB410 - good work! The point where you are getting stuck is in the introduction of a new element in the correct answer, that of "systems analyst," and you are not seeing a corresponding new element in the stimulus. But the stimulus did have a corresponding new element, and that was "last year". Let's try a slightly altered approach to the diagram, although yours was good:

Premise: NFCB Profit
Premise: PLYCB Profit
Conclusion: PLYCB NF

This is valid based on the conditional chain we could have built of PLYCB Profit NF

(PLY = Published Last Year)

Now to answer C:

Premise: PCMkt Bonus
Premise: PCSA Bonus
Conclusion: PCSA PCMkt

We get there the same way as above, through the contrapositive and the chain: PCSA Bonus PCMkt

Two chains, with a contrapositve, to get us our conclusion. The structure is the same in both arguments, and thus we have a winner!

Hope that helps!

Thanks, Adam!
Being able to recognize the new element cleared things up in the stimulus and the answer choice. Those conditional chains are manageable, but I imagine them to be a little challenging during test conditions. How would a high scorer solve this problem? I can imagine, if I were able to recognize the structure properly, being able to finish this question faster, or do high scorers go through the first 15-17 questions quicker so they have more than 1:20 on the final 8-10 questions? I only ask because I get through the first 15-17 getting 1-2 wrong, sometimes 0, but then perform miserably on the final 8. I usually get 5-6 wrong out of the final 8 either from rushing or running out of time. Do I need to develop the skill set to finish the first 15 questions quicker than the 1:20, so there is more time for the end?

@PB410

Dave Killoran has answered this question for us before, so I'm going to channel a lot of what he says about the ordering/difficulty of questions on LR.
Firstly, the easier questions tend to appear more frequently in the first half of the section. The following links address these patterns and will be helpful for you to review:
https://blog.powerscore.com/lsat/bid/15 ... Difficulty
https://blog.powerscore.com/lsat/bid/17 ... Difficulty
Thus, because each question has the same weight, but easier questions tend to take less time, if possible you'd prefer to work through all of the easier questions first. That allows you to build up correct answers and to typically build up extra time for later in the section (which can then be expended on the harder questions). Generally question difficulty tends to start jumping up around question 12.

However, keep in mind that the questions aren't ordered in exact order from easiest to hardest, so there will be easier questions later in the section just as on occasion there will be harder questions in the first half. Because of this, there's nothing wrong with skipping a question and returning to it later.

Missing questions at the end of the section isn't unusual at all. You are usually lower on time (and thus the pressure is higher), and as you can see from the articles I linked, the questions are usually harder at the end.

One last comment: if you have up to 10 minutes left in the section when you finish, you may be going a touch to fast on those harder questions.

I’m struggling to eliminate D.

My diagram is as follows

Under the umbrella of Waldville

James Benson → /Business
Maintains Business Files → Business

So we get

Maintain Business Files → Business → /James Benson

How come this doesn’t work? This argument seems to have the two factors as well.

#1 James Benson
#2 Maintains Business Files

lsatnoobie wrote:I’m struggling to eliminate D.

My diagram is as follows

Under the umbrella of Waldville

James Benson → /Business
Maintains Business Files → Business

So we get

Maintain Business Files → Business → /James Benson

How come this doesn’t work? This argument seems to have the two factors as well.

#1 James Benson
#2 Maintains Business Files

Can someone please help me with my above question? Thank you

lsat,

There are a few things lacking in answer choice (D). First, there is no temporal element in the second premise. The first premise says that something has never occurred. That matches the stimulus. The second premise states that something else has occurred in a certain time frame. Answer choice (D) lacks this. Also, as pointed out in the explanation, the stimulus has two categories of books, and answer choice (C) has two categories of employee, but answer choice (D) does not have these two categories.

Robert Carroll

Hi

I read the main explanation concerning the elimination of answer-choice D. Nevertheless, I still have two questions:
One, is my diagram of D correct?
And two, is my reasoning for eliminating D correct? (Not that I disagree with has been reasoned by the expert, but I am not able to comprehend it.)

D states:
"James Benson has never done business with the city of Waldville. Since Waldville only maintains business files on individuals that it does business with, it clearly does not have a business file on James Benson."

The first sentence is a premise symbolized as follows: ~B

The second sentence includes a rule and the conclusion.

The rule - "Waldville only maintains business files on individuals that it does business with" - is a conditional rule to which the sufficient condition is "Waldville only maintains files on individuals," and the necessary part is "it does business with."
The necessary part is symbolized as MF, and the sufficient as B.
And so the diagram and its contrapositive would respectively look as follows:
The Rule: MF------>B
Its Contrapositive: ~B----->~MF

The conclusion, the second clause of the second sentence is: "it clearly does not have a business file on James Benson." The conclusion is symbolized as: ~MF

In retrospect, the premise (or the first sentence), ~B, invokes the sufficient condition of the contrapositive, and concludes the ~MF.

Again, per my first question, please tell me is my diagram above correct?

Per my second question, my reasoning for eliminating D is that C is a closer match to the stimulus because both C and the stimulus trigger the rule with a premise that is temporally limited: "last year." D does not trigger the rule within a timely restriction. And it's not because both C and the stimulus used the exact temporal/timely limitation, "last year," within the premise, although that helped, but D uses no such time constraint within the premise that triggers the rule.

Otherwise, with the exception of the time constraint, all three arguments, the simulus, C, and D are valid and matching logically!

Is this time limitation a good reason for eliminating D?

If not, I, please, need someone to re-explain what the main explanation means but two "distinct types."

Thank You
Mazen

Hi

In previous post I typed necessary where I should've typed sufficient, and vice versa. I corrected my previous post so my questions would now may sense; I apologize!

I read the main explanation concerning the elimination of answer-choice D. Nevertheless, I still have two questions:
One, is my diagram of D correct?
And two, is my reasoning for eliminating D correct? (Not that I disagree with has been reasoned by the expert, but I am not able to comprehend it.)

D states:
"James Benson has never done business with the city of Waldville. Since Waldville only maintains business files on individuals that it does business with, it clearly does not have a business file on James Benson."

The first sentence is a premise symbolized as follows: ~B

The second sentence includes a rule and the conclusion.

The rule - "Waldville only maintains business files on individuals that it does business with" - is a conditional rule to which the sufficient condition is "Waldville only maintains files on individuals," and the necessary part is "it does business with."
The sufficient part is symbolized as MF, and the necessary as B.
And so the diagram and its contrapositive would respectively look as follows:
The Rule: MF------>B
Its Contrapositive: ~B----->~MF

The conclusion, the second clause of the second sentence is: "it clearly does not have a business file on James Benson." The conclusion is symbolized as: ~MF

In retrospect, the premise (or the first sentence), ~B, invokes the sufficient condition of the contrapositive, and concludes the ~MF.

Again, per my first question, please tell me is my diagram above correct?

Per my second question, my reasoning for eliminating D is that C is a closer match to the stimulus because both C and the stimulus trigger the rule with a premise that is temporally limited: "last year." D does not trigger the rule within a timely restriction. And it's not because both C and the stimulus used the exact temporal/timely limitation, "last year," within the premise, although that helped, but D uses no such time constraint within the premise that triggers the rule.

Otherwise, with the exception of the time constraint, all three arguments, the simulus, C, and D are valid and matching logically!

Is this time limitation a good reason for eliminating D?

If not, I, please, need someone to re-explain what the main explanation means but two "distinct types."

Thank You
Mazen