LR Question 15 Explanation
QUESTION TEXT: In a large residential building, there is a rule that no pets…
QUESTION TYPE: Necessary Assumption
CONCLUSION: The residents’ proposal to allow pets was voted down.
REASONING: The residents were trying to pass their proposal and failed.
ANALYSIS: The stimulus tells us that in order for there to be a vote, a petition must get the signatures of 10% of the residents. So for any proposal to be voted down it must first gather signatures. That is the necessary assumption.
It’s possible for the proposal to fail without a vote (if there aren’t enough signatures.)
___________
- CORRECT. If they didn’t do this, there could not be a vote.
- It is necessary that this did not occur. We needed 10% or more to sign.
- For a proposal to be voted down, only 50.1% of those who voted would have to be against it.
- If this were true, there is no way any proposal could lose once a vote were held since 10% support guarantees over 50% support in the vote. The argument requires that this answer choice not be true.
- This contradicts the stimulus. If they don’t get enough signatures there will be no vote.
Recap: The question begins with “In a large residential building, there is a rule that no pets”. It is a Necessary Assumption question. Learn how to master LSAT Necessary questions on the LSAT Logical Reasoning question types page.
More Resources for Necessary Assumption Questions
- Negations Article: Learn about negations on the LSAT.
- Conditional Reasoning Article: Learn about conditional statements.
- Negations Drill: Practice your negation skills.
- LR Diagrams Guide: Learn how to draw LR diagrams.
- Intro to Conditional Reasoning: Learn conditional reasoning basics.
- Intro Course lesson: This intro course lesson covers Necessary Assumption questions.
- Mastery Seminar lesson: This LR Mastery seminar lesson covers necessary assumption questions.
I’m a little confused by this one. The argument in notation is the following:
• Given: (new law succeeds) → (majority passed) → (vote was held) → (petition got 10% signatures)
• Given: the new law failed.
• Conclusion: the majority vote failed.
The argument is flawed because P → Q does not imply (not P) → (not Q).
The question asks, What is a necessary assumption for the argument? Honestly I’m not sure what they’re looking for. I mean, clearly in order to conclude that the majority vote failed, there needed to be a vote in the first place, which requires a petition with 10% signatures. This is given information.
But the mere fact of completing a 10% signature petition does not fix the argument. All we know is that a majority vote is necessary for the law to pass, not that it’s sufficient. Maybe the landlord has a veto power or something. This is entirely within the bounds of the question.
I guess I’m confused because usually in the LSAT you’re fixing a flawed argument. But here the correct answer does absolutely nothing to fix the argument. It just makes it “less wrong,” which is still a wrong argument.
How am I supposed to think about this differently? Is this the difference between sufficient assumption and necessary assumption questions?
Good question! The key is about what they’re asking. We’re not supposed to fix the argument. We’re just supposed to allow it to be possible.
So, there are two ways to fail to change the law:
1. Not even get 10% of signatures. Total failure
2. Get 10%, get it put to a vote, lose the vote
The author assumes the 2nd one happened. If that’s the case, then they must assume the pet lovers didn’t fail in the first, most basis way: by simply not getting enough signatures.
Hope that helps!