LR Question 10 Explanation
QUESTION TEXT: All of John’s friends say they know someone who has smoked…
QUESTION TYPE: Must be True
FACTS: John’s friends all claim to know a long term, healthy smoker. John doesn’t and is certain at least some of his friends do not know any long term smokers either.
ANALYSIS: We’re told to assume that all statements in the passage are true. That means that John is correct. If John is correct then at least some of his friends do not know any such smoker. They may be mistaken (rather than lying), but they are not telling the truth.
___________
- We don’t know about smokers. We only know about John’s friends.
- We don’t know if John’s friends have exaggerated or lied.
- We know some of John’s friend don’t know such a smoker. But as for the rest of his friends we don’t know whether they all know the same smoker or different smokers.
- This is possible, but it doesn’t have to be true. John doesn’t say how many friends he knows aren’t telling the truth.
- CORRECT. Yes. If John is correct that he is not unique in not knowing a smoker then at least some of his friends are not being truthful.
Recap: The question begins with “All of John’s friends say they know someone who has smoked”. It is a Must be True question. Learn more about LSAT MBT questions in our guide to LSAT Logical Reasoning question types.
More Resources for Must Be True Questions
- Conditional Reasoning Article: Learn about conditional statements on the LSAT.
- LR Diagrams Guide: Learn how to draw LR diagrams.
- Intro to Conditional Reasoning: This intro course lesson covers conditional reasoning basics.
- Intro Course lesson: This intro course lesson covers Must Be True questions.
- Mastery Seminar lesson: This LR Mastery seminar lesson covers must be true questions.
Hi, I selected E because it is the best of the answers, but I don’t think it needs to be true. Assuming the statements are true means that it is true that John is certain. That is not the same as assuming that John is right. I think this is a bad LSAT question. Someone please tell me if I’m missing something.
This is definitely something you can problematize, and where I may add some disagreement with Graeme’s explanation, or at least add further nuance.
The stimulus says “it is quite certain”, not “he is quite certain”. Graeme notes that John is certain, but I would interpret this to mean that the narrator is asserting a fact. So, at least one of John’s friends is also in the same position as John (i.e. does not know such a person).
And given that we’re asked to assume that all the statements in the stimulus are true, we can take it for a fact that it IS quite certain this is the case. Hopefully that helps! Let me know if you disagree or have further questions.