PrepTest 149

Incorrect. The conclusion here talks about an apartment on the 4th floor—in other words, it talks about something that doesn't meet either sufficient condition from the premises instead of the necessary conditions.

Incorrect. Above 4th floor → 2-3 bedrooms
Below 4th floor → 0-2 bedrooms . . . we can eliminate this answer because there's overlap between the two necessary conditions (2 bedrooms) while there's no such overlap in the stimulus. (Additionally, the conclusion talks about apartments on the fourth floor or higher, which overlaps with the sufficient condition of the first conditional.)

Correct. Argument or Facts:
Argument

Valid or Flawed:
Valid

Question Type:
Parallel Reasoning

Stimulus Summary:
New car in Rollway Motors lot → Over $18k
10+ year old car in Rollway Motors lot → Under $5k
Therefore Ð not Over $18k and not Under $5k → not New and not 10+ years old

Answer Anticipation:
This answer uses an interesting conditional structure. It establishes two conditionals, takes the contrapositive of each, and then mashes them together despite not having terms that overlap.

However, it is valid. The contrapositive of the first statement establishes that a car that costs less than $18k isn't new (so it's used), and the contrapositive of the second tells us that if a car costs at least $5k then it's not 10+ years old. So if a car meets both of those sufficient conditions, then it will also meet both of those necessary conditions.

This analysis, however, isn't necessary to get the question correct. Instead, we can find an answer that follows the same form:

A → B
C → D
Therefore: not B and not D → not A and not C

In short, we need an answer that establishes two conditionals, and then concludes that something not meeting either necessary condition doesn't meet either sufficient condition.

Answer Explanation:
Above 4th floor → 3+ bedrooms
Below 4th floor → 0-1 bedrooms
Therefore Ð 2 bedrooms (i.e., not 3+ bedrooms AND not 0-1 bedrooms) → 4th floor

This answer establishes two conditionals, and then it mashes the contrapositives together. While it uses a single term (2 bedrooms) to trigger the sufficient condition of both contrapositives, it still follows the same valid logical structure, and so this is the correct answer.

Key Takeaway:
While not particularly common, a facet of this stimulus shows up frequently enough that you should take note. There are a lot of numbers thrown around, both in the stimulus and the answer choices. These numbers are frequently set as minimums/maximums—more than $18k; less than $5k; above the 4th floor; no fewer than 3 bedrooms. When numbers are given as limits, make sure you stop for a second and ensure that you know what it's saying.

In particular, note if it's inclusive or note. What we mean by that is the difference between "at least $18k" and "over $18k." The former is inclusive—it includes $18k. The latter, however, isn't, because something that costs $18k doesn't count as costing "over" $18k. When this language is used—especially in Parallel Reasoning questions—mismatches in that language can be key to finding the correct answer, or at least eliminating some incorrect answers.

Incorrect. Above 4th floor → 0-2 bedrooms
Balcony → 3 bedrooms
Therefore Ð Balcony → not Above 4th floor

This argument is valid, but it chains the second conditional with the contrapositive of the first, so it follows a different structure.

Incorrect. Above 4th floor → 3+ bedrooms
4th floor or under → not Vacant . . . and we're out because the sufficient conditions here cover all of the floors, leaving open no "middle ground" as in the stimulus.