Logical Reasoning · Flaw
PrepTest 151 · Section 2 · Question 3
Phase 1 (your first ~400 questions): read the guidance, then answer. No clock.
Step 1 · Pre-Question Guidance · read this first
- “if”
- “soon”
- “will”
- “end result”
Playground logic
Grandpa's top bun says no late bedtime tonight. His patty is a chain of 'then this will happen' links. The flaw is treating that one chain as the only way things could go.
Step 2 · The kid story
Ten Minutes Past Bedtime
Tommy asked to stay up ten extra minutes to finish his comic. Grandpa crossed his arms. "If I say yes tonight, you'll ask every night. Then Lulu will want it too. Soon nobody in this house will have a bedtime. Then you'll both be grumpy at school, and Ms. Rivera will call me!" Tommy blinked. "It's ten minutes, Grandpa." Lulu raised her clipboard. "I drew the chain. Yes tonight, then every night, then me, then no bedtime, then grumpy, then a phone call. But every arrow is just a maybe. Maybe Tommy only asks once. Maybe you say no tomorrow." Grandpa scratched his chin. "You could have just said I was being dramatic." "I said it with arrows," said Lulu.
Step 3 · Try the model question
Grandpa says Tommy should not get ten extra minutes tonight. If he says yes, Tommy will ask every night, then Lulu will ask too, and soon no one will have a bedtime. In the end, both kids will be grumpy at school.
Which choice best describes a weakness in Grandpa's reasoning?
Step 4 · The courtroom tale
The Lemonade Domino
"Your Honor," boomed the city's lawyer, "if we let this child sell lemonade on the corner, next week ten kids will sell lemonade. Then the ice cream truck will leave town. Then summer will be ruined!" Mr. Whitfield rose slowly. "Your Honor, my opponent has built a tower of dominoes and swears they will all fall. But maybe nobody else sets up a stand. Maybe the truck stays because people get thirsty for ice cream after lemonade. He has shown one way things might go and called it the only way." The judge nodded. "One domino is not a whole row. Permit granted." The young seller cheered and offered everyone a cup.
Step 5 · Work the real question
Open PrepTest 151, Section 2, Question 3 in your official copy from LSAC (for example in LawHub) and read it there.
Your answer
How to apply it
Map the argument as a chain of steps from the first event to the final bad result. Ask whether each step must happen, or only might. If the arguer treats a series of possible results as the only outcome, the flaw is a slippery slope. Pick the choice that describes that. Reject choices naming flaws that need pieces the argument lacks, such as a repeated premise or a timing reversal.