PrepTest 123

[lcid:3589] Prep Test 123 LSAT — Logical Reasoning — S2 Logical reasoning

Question prompt

Standard aluminum soft-drink cans Remaining source text redacted.
Why the credited answer is right

Credited answer: C

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

Strengthen with Sufficient Premise Questions

Stimulus Summary

Aluminum cans M are made from 50% recycled materials from aluminum cans L. All L were recycled into M. Aluminum cans are essentially all aluminum. Therefore, there are twice as many M cans as L cans.

Answer Anticipation

The conclusion of this argument is a relative number—twice as many. That's based on each M can being 50% L can (and 50% aluminum from another source). Since all of L went into making M, it seems as if each M can being only 50% L would mean you could get twice as many cans. So where's the flaw?
Well, in order to get twice as many cans, we'd have to get all of the aluminum from each can. While the stimulus states that all of the L cans were recycled into M cans, it's easy to assume that there wasn't any waste, but maybe recycling a can only yields half as much aluminum as went into it. Without knowing how much of L cans we can recover in the recycling process, it's impossible to know how many M cans we can make at 50% each. Only if we get essentially all of the aluminum from each L can will we double the number of cans when making M.
That said, it can be difficult to anticipate this answer. Don't get too hung up on an anticipation—if you're spinning your wheels, head to the answers and find ones that are in scope.

Answer choices

  1. A
    The aluminum in the Remaining source text redacted.
    Why choice A is not credited
    Incorrect. The argument only cares about how many M cans we were able to make, so it doesn't matter what happens to those cans. This answer is out of scope.
  2. B
    Recycled aluminum is of Remaining source text redacted.
    Why choice B is not credited
    Incorrect. The quality doesn't matter, just the number of cans we can make. This answer choice is out of scope.
  3. C
    All of the aluminum Remaining source text redacted.
    Why choice C matches the stem
    Correct. This answer choice deals with the recycling process, telling us that 100% of the aluminum is recovered for recycling. If that's true, then recycling all L cans into M cans at 50% L per M can will allow twice as many M cans to be made, and our argument is valid. This is the correct answer.
  4. D
    None of the soft-drink Remaining source text redacted.
    Why choice D is not credited
    Incorrect. The transition from L to M matters. Since we don't know anything about what happened before the L cans were made, and there's no information in the stimulus about recycled cans being more or less recyclable, this answer is out of scope.
  5. E
    Aluminum soft-drink cans are Remaining source text redacted.
    Why choice E is not credited
    Incorrect. Other materials and the ease of recycling are out of scope of the argument. Recycling L cans into M cans is the only consideration.

What this tests

Discussion

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