Logical reasoning PrepTest 130 · Section 1 · Question 25

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen with Sufficient Premise

Stimulus Summary:
Handmade components → More expensive than no handmade components
Made-to-measure → Medium-priced to expensive
~Human hair → ~Handmade foundation
Human hair → Dry-cleaned
Therefore: Made-to-measure → Dry-cleaned

Answer Anticipation:
That's a lot more than we ever thought we'd know about wigs! Since there's so much going on here, we really should start with the terms in the conclusion and start building our chain from there. At the end of the day, we need to start with Made-to-measure and build a chain to Dry-cleaned. Both of those terms show up in premises, so the gap will be between premises here—a rarity compared to gaps between the premises and conclusion, but something we can still handle!

Let's start with the sufficient condition of the conclusion: Made-to-measure. Looking at our premises, we can see that that condition guarantees that the wig is Medium-priced to expensive. And while that term is related to the necessary condition of the first premise, it's not the same, so we can't draw an inference. "More expensive" is a relative term, and Medium-priced to expensive is not, so we're stuck there building from the sufficient condition:

Made-to-measure → Medium-priced to expensive → (???) → Dry-cleaned

Now that we've hit a dead end there, we need to build to Dry-cleaned. We know, from the premises, that a wig having Human hair guarantees it needs to be dry-cleaned. And taking the contrapositive of that third conditional, we know that having a Handmade foundation guarantees a wig has human hair. And while a Handmade foundation is a Handmade component, both of those terms are now sufficient conditions, so we can't chain them together. That makes our argument now:

Made-to-measure → Medium-priced to expensive → (???) → Handmade foundation → Human hair → Dry-cleaned

With the premises built from the sufficient condition and to the necessary condition of the conclusion, we can see where the gap is—between Medium-priced to expensive and Handmade foundation. The correct answer should fill that gap:

Medium-priced to expensive → Handmade foundation
not Handmade foundation → not Medium-priced to expensive

Answer Explanation:
Medium-priced to expensive → Handmade foundation. This answer is the gap that we found in the argument after building connections to the terms in our conclusion, so this is our answer.

Key Takeaway:
Who has time to do all that work in the Anticipation step? Anyone who wants to be able to fly through the answers and find the correct one efficiently. Without doing that work up front, you'll be drawing out conditionals and making connections for each answer choice, which will take a lot more time. Doing that work up front allowed us to know exactly what we were looking for in an answer, which means we should be able to find the correct answer within 10-20 seconds of moving to the answer choice analysis step.

Incorrect. Handmade foundation → More expensive than wig without handmade foundation. This answer applies the first conditional to a specific component, but it doesn't form the connection that's missing from the argument.

Incorrect. Handmade component → Dry-cleaned. The argument already connects wigs with a handmade foundation to a need to be dry-cleaned, so this answer choice still fails to connect Made-to-measure wigs to dry-cleaning.

Incorrect. Handmade foundation → Medium-priced to expensive, but it's the reverse of the connection we're looking for.

Incorrect. Dry-cleaned → Handmade foundation. Using the premises of the argument, it's already been established that any wig with a handmade foundation should be dry-cleaned, so this answer establishes the reversal of something we already know—it doesn't connect terms that need to be connected.