Logical Reasoning · Parallel Flaw
PrepTest 145 · Section 2 · Question 5
Phase 1 (your first ~400 questions): read the guidance, then answer. No clock.
Step 1 · Pre-Question Guidance · read this first
- “linked to”
- “does not change”
- “so”
Playground logic
Marcus says his reading score is tied to the books on his shelf, the shelf never changes, so his reading score can never change. X-Ray it: link, fixed partner, 'so it's frozen'. The flaw: reading also depends on practice, sleep, and a hundred other things.
Step 2 · The kid story
Marcus and the Frozen Reading Score
Marcus slammed down his report card. "My reading score is connected to the books on my shelf. Everyone knows that. And my shelf has had the exact same twelve books since second grade. So my reading score can never change. It is scientifically frozen." Lulu tapped her clipboard. "Your score is connected to your shelf. Okay. But it is also connected to how much you read, whether you go to the library, and whether you sleep or play video games all night." Priya added, "Being linked to one fixed thing does not mean nothing else can move it." Marcus frowned. "So if I read more library books..." "Your score can still change," said Lulu. Marcus picked up a library card, suspiciously.
Step 3 · Try the model question
Marcus: My reading score is connected to the books on my shelf. The books on my shelf never change. So my reading score will never change.
Which choice makes a mistake with the same shape as Marcus's mistake?
Step 4 · The courtroom tale
The Case of the Unchangeable Rent
The shop tenant's lawyer stood. "Your Honor, the rent on this shop is tied to the size of the building. The building has been the same size for forty years. Therefore the rent can never change, and the landlord's increase is void." Mr. Whitfield, for the landlord, snapped his suspenders. "Counsel proves the rent is linked to one fixed thing. But rent is also tied to taxes, the lease terms, and the neighborhood, and those move all the time." The judge nodded. "Being linked to one thing that stays put does not lock a thing in place. Other links can still move it. The increase stands."
Step 5 · Work the real question
Open PrepTest 145, Section 2, Question 5 in your official copy from LSAC (for example in LawHub) and read it there.
Your answer
How to apply it
X-Ray the stimulus: something is said to be linked to a second thing, the second thing stays the same, and the conclusion says the first thing stays the same too. Strip away topic. Check each answer for that exact skeleton and the same gap (the first thing could depend on other factors). Reject answers that reach a fully valid conclusion, answers that predict change, and answers with a different move, like a cause-to-cure jump.