LSAT 131 | Section 2 | Logical Reasoning: Q9

LR Question 9 Explanation

QUESTION TEXT: No member of the Richardson Theatre is both a performer

QUESTION TYPE: Flawed Parallel Reasoning

CONCLUSION: Leon and Marta must be performers.

REASONING: You can’t be both an administrator and a performer. Leon and Marta aren’t administrators.

ANALYSIS: This argument gives us a “not both” statement. It then incorrectly uses that to prove someone is one of the two.

You can’t do that. Here’s a parallel argument:
“A food can’t be both meat and vegetable. This apple is not meat, so it is a vegetable.”

All of the answers use the same vocabulary, so it’s very important to be clear on the structure before you start.

___________

1. I skipped this right away when I saw “not all”. That doesn’t match the structure of the stimulus. (I didn’t eliminate it, I just considered other answers first.)
   This is a good argument. It says there are some non-salaried employees (e.g. work on commission). It then lists two salaried employees: so there must be others.
2. The start of this is similar, but this is a good argument! Ms. Walsh meets the sufficient condition of the conditional.
3. CORRECT. This matches exactly. We could write the evidence as:
   Mexico → Canada
   The author then incorrectly concludes “Canada” by incorrectly negating the evidence to be:
   “Mexico → Canada”
4. This is a good argument! You can’t represent both. Since Ms. Tseung represents one, she therefore doesn’t represent the other.
5. This is a good argument! Both boards have at least five members, and there is no overlap. So the combined total is ten or larger.