PrepTest 113
[lcid:3549] Prep Test 113 LSAT — Logical Reasoning — S2
Logical reasoning
Question prompt
Joan got A's on
Remaining source text redacted.
Why the credited answer is right
Credited answer: B
The notes below walk through why it fits the stem and how to eliminate the rest.
Question Type
Errors in Reasoning Questions / Sufficient & Necessary Questions
Answer choices
-
Aignores the possibility that Remaining source text redacted.
Why choice A is not credited
Incorrect. The argument doesn't ignore this possibility—it assumes it. It argues that since she didn't get an A on the term paper, then she must do the presentation to pass. In other words, she must either get an A on the term paper or do the presentation. -
Bpresupposes without justification that Remaining source text redacted.
Why choice B matches the stem
Correct. Argument or Facts:
Argument
Valid or Flawed:
Flawed
Question Type:
Errors in Reasoning
Stimulus Summary:
Joan - A's on all homework
A on term paper → Pass without doing presentation
not A on term paper
Therefore - not Pass without doing presentation
Answer Anticipation:
This argument involves conditional logic, and any Errors in Reasoning question with conditional logic is likely to have a conditional logic flaw, so we should start by analyzing that.
First, the conditional premise. It does have two keywords—"if" and "without." In general, when there are two keywords like this, use "if" and treat the "without" as part of the condition it's included in, which is what we did here.
With that noted, we can see that the argument establishes that Joan didn't meet the sufficient condition of the conditional, and then it concludes that she didn't therefore achieve the necessary. However, that's an illegal negation—there might be other sufficient conditions to passing without doing a presentation. Let's find an answer that points out this conditional logic flaw.
Answer Explanation:
This answer describes an illegal negation. It assumes ("presupposes without justification") that Joan's not meeting the sufficient condition of the conditional premise ("not getting an A on her term paper") means she doesn't achieve the necessary condition ("prevent her from passing the course without . . . the presentation."). This answer is therefore correct.
Key Takeaway:
When an Errors in Reasoning question features conditional logic, your first check should be for conditional logic flaws. -
Coverlooks the importance of Remaining source text redacted.
Why choice C is not credited
Incorrect. It doesn't overlook the importance—it establishes the presentation as pretty key to a course grade if the person doesn't get all A's on homework and the term paper! -
Dignores the possibility that Remaining source text redacted.
Why choice D is not credited
Incorrect. The argument establishes that Joan didn't get an A on her term paper, and it's the contrapositive of the conditional in the stimulus, so this answer is not something the argument ignores. -
Efails to take into Remaining source text redacted.
Why choice E is not credited
Incorrect. Joan didn't get an A on her term paper, so what is true of those students doesn't apply here.
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