LSAT 131 – Section 2 – Question 19

LSAT 131 - Section 2 - Question 19

December 2009

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT131 S2 Q19
+LR
Must be true +MBT
Conditional Reasoning +CondR
A
1%
152
B
9%
161
C
74%
166
D
1%
158
E
15%
157
145
154
163
 +Harder 147.936 +SubsectionMedium

J.Y.’s explanation

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At a gathering at which bankers, athletes, and lawyers are present, all of the bankers are athletes and none of the lawyers are bankers.

Summary
The stimulus can be diagrammed as follows:

Notable Valid Inferences
Some of the athletes are not lawyers.
Some of the people who are not lawyers are athletes.

A
All of the athletes are bankers.
Could be false. (A) confuses the necessary and sufficient conditions: we know that all the bankers are athletes, but the opposite is not necessarily true. Maybe there are 100 athletes and 50 bankers, in which case the bankers are still athletes, but many athletes aren’t bankers.
B
Some of the lawyers are not athletes.
Could be false. (B) has a negation problem: our diagram shows that some athletes are not lawyers, but that’s not the same thing as “some lawyers are not athletes.” What if, for example, there are 100 athletes and 50 lawyers, and every lawyer is an athlete?
C
Some of the athletes are not lawyers.
Must be true. As shown below, chaining the conditional claims yields a valid argument with the conclusion “some athletes are not lawyers.” In other words, we know that there are bankers at the gathering, and we know that those bankers are people who are athletes but not lawyers.
D
All of the bankers are lawyers.
Must be false. The stimulus says that none of the lawyers are bankers, which, by the contrapositive, means that none of the bankers are lawyers!
E
None of the lawyers are athletes.
Could be false. While we know that not all of the athletes are lawyers, we don’t know anything about the percentage of lawyers who are or aren’t athletes. Maybe, for example, there are 100 athletes and 50 lawyers, and every lawyer is an athlete! Or 20 of the lawyers are athletes!

We have an MBT question which we can glean from the question stem which reads: If the statements above are true, which one of the following statements must also be true?

We’re told there are 3 sets of people at this gathering: bankers, athletes, and lawyers. Sounds like a pretty nice gathering! Then we get a pair of very straightforward conditional statements that we can map out: Bankers→Athletes and Lawyers→/Bankers. So what do we know about our three categories of attendees? If you’re a banker then you are definitely an athlete and you are definitely not a lawyer. If you are a lawyer you are definitely not a banker. And if you’re an athlete—well, we don’t know much. We know that all bankers are athletes, and therefore some athletes are bankers. We can’t say anything more than that.

This question is a test of your ability to understand conditional logic. There’s not much more to break down about this stimulus. I suppose we could spend more time asking questions about this gathering—where is it being held? Who are these hybrid banker/athletes? What are these titans of industry and sport gathering to discuss? But that’s not really what you’re here to learn about, so let’s move onto the answer choices:

Answer Choice (A) We know all the bankers are athletes, but if you know your conditional rules, you know that we can’t simply flip this around without negating both sides. This is a very simple case of sufficiency/necessity confusion. Case closed! Moving on.

Answer Choice (B) We know that none of the lawyers are bankers. Other than that, we have no information to go off of. This is wholly unsupported.

Correct Answer Choice (C) Here we go! If you think back to our analysis of the stimulus we concluded that some athletes are bankers. What do we know about bankers? They are definitely not lawyers. Therefore some athletes are not lawyers. Simple as that!

Answer Choice (D) This is just the opposite of what we know to be true. No bankers are, in fact, lawyers.

Answer Choice (E) We don’t know anything about the relationship between lawyers and athletes so we cannot conclude anything about whether there are or are not any lawyers who are athletes.

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LSAT PrepTest 131 Explanations

Section 1 - Logical Reasoning

Section 2 - Logical Reasoning

Section 3 - Logical Reasoning

Section 4 - Reading Comprehension

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