LR Question 18 Explanation
QUESTION TEXT: If there are any inspired musical performances in the…
QUESTION TYPE: Must be True
FACTS:
Inspired musical performance ➞ good show ➞ sophisticated listeners in the audience ➞ understand your musical roots.
CONTRAPOSITIVE:
If nobody in the audience understands their musical roots ➞ then there are no sophisticated listeners in the audience ➞ no good show ➞ no inspired musical performances.
ANALYSIS: This is a question where drawing really helps. For a “formal logic” must be true question, the answer will either come from the original sufficient-necessary diagram chain or its contrapositive. So you really need to be clear on those to be able to answer it.
It’s quite possible to do it mentally. But if you have any trouble on these questions then make drawings until you get used to the logic.
___________
- CORRECT. This is shown by the contrapositive.
- This is an incorrect negation.
- This is an incorrect reversal.
- We only know that there will definitely be a good show if there is an inspired musical performance. Even if there are sophisticated listeners there might be no inspired performance or good show.
- This is an incorrect reversal.
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.
This is interesting. The analysis mostly correct, but this question is very poorly written. The sentence “If there are any inspired musical performances in the concert, the audience will be treated to a good show” describes a sufficient condition, not a necessary one.
Even one inspired musical performance is sufficient to make the show good. Does that mean that without an inspired musical performance, the show can’t be good? NO. That would be true if this was a necessary condition, but it isn’t. There might be a million other sufficient conditions for a good show, and the absence of any one of them does not tell us whether the show is good or not.
The question as written has no solution, and should never be used on a test or in practice.
I see where you’re coming from, but I think you’ve misapplied the sufficient/necessary distinction here. You’re right that “If there are any inspired performances, there will be a good show” makes an inspired performance sufficient for a good show, not necessary. That means we can’t conclude, from this statement alone, that no inspired performances = no good show.
But it’s not asking us to draw that conclusion from the first premise in isolation. The second premise adds: “There will not be a good show unless there are sophisticated listeners.” That makes sophisticated listeners necessary for a good show. When you chain that, you get: “inspired performance -> good show” and “good show -> sophisticated listeners”, therefore: “inspired performance -> sophisticated listeners.”
And if inspired performances require sophisticated listeners, then by contrapositive, “no sophisticated listeners -> no inspired performances”. That’s answer A, so the inference follows.
You’re right. I tried to edit my comment right after I left it but couldn’t figure out how to.
That’s okay! I think it’d be helpful to other students to leave it up as necessary/sufficient is a common confusion.
Thank you!!! I was going absolutely crazy trying to figure out why D is incorrect and you summed it up so clearly. Thank you.
Happy to help! For future reference, D is what’s called an Incorrect Reversal
Thank you!!! I was going absolutely crazy trying to understand why D was incorrect and you summed it up so clearly. Thank you.