Logical reasoning PrepTest 101 · Section 2 · Question 5

Question prompt

Altogether, the students in Remaining source text redacted.
Why the credited answer is right

Credited answer: D

The notes below walk through why it fits the stem and how to eliminate the rest.

Argument or Facts

Argument

Valid or Flawed

Flawed

Question Type

Flawed Parallel Reasoning Questions

Stimulus Summary

Ms. T’s class collected the most aluminum cans, so the student who collected the most must be in her class.

Answer Anticipation

Knowing the common errors in reasoning is key to doing well on the LR section of the LSAT, and this is a great example of one of those common flaws.
Here, the premise compares Ms. T’s class to all other classes. From that, it draws a superlative conclusion about a specific student in her class. That’s jumping from something that’s true of a whole to saying it’s also true of a part of that whole - a classic Part vs. Whole flaw.
Here, it’s possible that Ms. T’s students each collected an above-average number of cans, but there was one superstar in another class that collected the most, while the rest of the students in that class collected none. In that case, the student who collected the most cans would not be in the class that collected the most cans.
Let’s find an answer that commits a similar Whole to Part flaw (the specific version of the flaw present here, since the premise is about the class/whole and the conclusion is about the student/part).

Answer choices

  1. A
    Altogether, more trees were Remaining source text redacted.
    Why choice A is not credited
    This argument is valid, and it also compares only three classes, not all classes. And it compares the total of those classes combined, not individually, as the stimulus did.

  2. B
    More than half of Remaining source text redacted.
    Why choice B is not credited
    This argument makes an overlapping sets flaw - it assumes that there isn’t enough overlap between the two groups to mean some students fall outside of it. That’s a separate flaw.

  3. C
    Mr. Rowe's Milton Elementary Remaining source text redacted.
    Why choice C is not credited
    This argument compares only two groups, and it doesn’t draw a superlative conclusion. This argument is flawed in that it assumes something about the relative cost of candy bars and raffle tickets, not that there’s a connection between a whole and the parts that make it up.

  4. D
    The total number of Remaining source text redacted.
    Why choice D matches the stem
    If you replace “tickets to the school fair sold” with “aluminum cans collected,” this argument is exactly the same as the one in the stimulus, going from what is true of a whole (Ms. R’s class selling the most tickets) to a part of that whole (the student who sold the most tickets). This answer is therefore correct.

  5. E
    Ms. Ventura's Milton Elementary Remaining source text redacted.
    Why choice E is not credited
    The conclusion of this argument is about the average, not a single student, so it doesn’t commit a Part vs. Whole flaw. In fact, this argument is valid, as fewer students making more birdhouses must have, on average, made more birdhouses per student than the other classes.

What this tests

Question analytics

Based on historical answer selection rates for this question.

Answer choice distribution

  1. A 5%
  2. B 1%
  3. C 2%
  4. D Credited 91%
  5. E 2%

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