LSAT 106 | Section 2 | Logical Reasoning: Q15

LR Question 15 Explanation

QUESTION TEXT: Rhonda will see the movie tomorrow afternoon only if…

QUESTION TYPE: Parallel Reasoning

CONCLUSION: Rhonda won’t see the movie.

REASONING: Ted won’t go to the concert. That means that Paul won’t go to the concert. And Rhonda will only go to the movie if Paul goes to the concert.

ANALYSIS: This is a good argument. It joins two sufficient-necessary statements and reasons using the contrapositive:

Rhonda movie ➞ Ted concert ➞ Paul concert

Paul doesn’t go ➞ Ted doesn’t go ➞ Rhonda doesn’t go

___________

1. This is a bad argument. Finding a babysitter was a necessary condition for Janice visiting but it wasn’t a sufficient condition.
2. CORRECT. This is a good argument. Gary does laundry ➞ peter has to work ➞ Cathy ill. Since Cathy isn’t ill, we can use the contrapositive to show that Gary won’t do laundry.
3. This is a bad argument. The market having trout was a sufficient condition for barbecuing fish, but not a necessary condition. Kelly might just decide to barbecue some other kind of fish.
4. Bad argument. One of Lisa’s brothers attending was a necessary condition but not a sufficient condition.
5. First, Mark postponing his appointments is a necessary condition, not a sufficient condition. Second, Mark postponed “some” of his appointments. That could mean “most”, but we don’t know.

Recap: The question begins with “Rhonda will see the movie tomorrow afternoon only if”. It is a Parallel Reasoning question. Learn how to master LSAT Parallel questions on the LSAT Logical Reasoning question types page.