Logical reasoning PrepTest 106 · Section 1 · Question 20

Question prompt

If the economy is Remaining source text redacted.
Why the credited answer is right

Credited answer: A

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

Argument or Facts

Facts

Valid or Flawed

NA

Question Type

Cannot Be True Questions / Sufficient & Necessary Questions

Stimulus Summary

Economy weak → Prices constant AND Unemployment rises
Unemployment rises → Investment decreases
~Investment decreases

Answer Anticipation

When we’re dealing with Cannot be True questions, we’re reading the stimulus to find statements that can be contradicted in the answer choices, as we need an answer that contradicts the stimulus. Normally, we’d see conditional statements and rely on them - an answer that establishes the sufficient condition but then says the necessary condition isn’t present would contradict the conditional and be correct.
Here, however, we’re in a little bit of a different situation. That last statement is a nonconditional one that intersects with the conditional statements. As such, we can draw some inferences based on that.
Let’s start with our diagram. The opening line uses the most common conditional keyword - “if,” signifying a sufficient condition. However, it is a bit tricky in that it uses “although” as an AND linkage in the necessary condition (we can tell it’s an AND because both of those things are true in a weak economy). The second one uses “only if,” a necessary condition indicator.
With that noted, and with the final line read, we can see that we need to take the contrapositive of the second conditional to draw an inference:
~Investment decreases → ~Unemployment rises
So based on that conditional and the final line, we can infer ~Unemployment rises.
That intersects with the contrapositive of the opening line, so let’s take that (remembering that AND becomes OR when contraposing):
~Prices constant OR ~Unemployment rises → ~Economy weak
Since we already inferred that ~Unemployment rises, this conditional allows us to infer ~Economy weak.
With our two inferences, we should head to the answer choices to find one that says either of these isn’t present, since we know that they are:
~Unemployment rises. ~Economy weak.

Answer choices

  1. A
    Either the economy is Remaining source text redacted.
    Why choice A matches the stem
    Either/or statements can be read as at least one on the LSAT, so this answer says that at least one of these is true: Economy weak OR Investment decreasing. This would be false, therefore, if neither of these is true. The last line tells us that investment isn’t decreasing, and that allows us to conclude that the economy isn’t weak, based on the two conditionals (as we walked through in our anticipation). Since neither of these things is true, it must be false that at least one of them is, making this our answer.
  2. B
    If unemployment rises, the Remaining source text redacted.
    Why choice B is not credited
    The stimulus doesn’t connect unemployment rising and prices remaining constant in a conditional - they’re both included in the same condition in the first conditional. Since there’s no direct relationship between these two, this answer could be true, so we can eliminate it.
  3. C
    The economy is weak Remaining source text redacted.
    Why choice C is not credited
    This answer combines the two conditionals. Remember, we can split up AND necessary conditions since both are individually true. The first conditional, then, tells us that Economy weak → Unemployment rises, and the second chains with that, guaranteeing that investment decreases. As such, the chain says Economy weak → Investment decreases, matching this answer. Since it must be true, we can eliminate it.
  4. D
    Either the economy is Remaining source text redacted.
    Why choice D is not credited
    We talked about Either/Or statements in answer choice (A), so we’re going to take a different tack here to give you more tools to work with! An either/or statement talking about A and B can be diagrammed as ~A → B (this comes up a lot in the LG section). So let’s treat this answer as ~Economy weak → Prices constant. The relationship between these two in the stimulus is Economy weak → Prices constant. These two statements don’t contradict each other, so this answer doesn’t have to be false. (To contradict a conditional with another conditional, you keep the sufficient condition the same but negate the necessary condition; this does the opposite.)
  5. E
    Either unemployment is rising Remaining source text redacted.
    Why choice E is not credited
    Let’s use the same method here as in (D), and view this answer as: ~Unemployment rising → ~Economy weak. We actually know that this is true based on the contrapositive of the first conditional, so we can eliminate this answer.

What this tests

Question analytics

Based on historical answer selection rates for this question.

Answer choice distribution

  1. A Credited 45%
  2. B 6%
  3. C 13%
  4. D 19%
  5. E 17%

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