Logical reasoning PrepTest 127 · Section 2 · Question 19

Correct. Argument or Facts:
Facts

Question Type:
Must Be True

Stimulus Summary:
(1) Literature → not Physics
(2) Physics-some-Art
(3) Rhetoric → not Physics

Answer Anticipation:
This is a clear example of a Must Be True question that's focused on making inferences from conditionals and quantified statements, so we need to brush off those skills. First up, we need to get a shared term in as many statements as possible so that we can combine them. Here, since we can contrapose the conditionals, but we can't change up the some statement, we should take the contrapositive of statements 1 and 3 so they all talk about students who are taking Physics:

(1) Physics → not Literature
(2) Physics-some-Art
(3) Physics → not Rhetoric

From here, since there are only 3 statements, we can make our inferences up front and be prepared for any potential correct answer. Remember that an easy way to tell if two statements lead to an inference is to compare how much of the shared term is discussed—conditionals talk about 100% of the sufficient condition, and some statements talk about at least 1%. If the two statements combine to talk about over 100% of a given group, then there must be some overlap in the members being discussed. Using that as a guide, we can make the following inferences:
1+2) not Literature-some-Art
1+3) not Literature-some-not Rhetoric
2+3) Art-some-not Rhetoric

Answer Explanation:
Since no students in physics are taking literature, and some students in physics are taking art, there must be some students in art who aren't in literature—those physics students. This is inferable.

Key Takeaway:
Inferring from quantified statements is a specific skill that the LSAT tests a couple times per test. You can either practice it and get these questions correct quickly, or you can fail to do so and have a _ shot at getting these right. We think the correct path is clear.

Incorrect. To get a conditional answer, we'd need to work exclusively with conditionals. Here, to make an inference about students in art, we have to work with the some quantified statement, which means this answer is too strong.

Incorrect. We know there are some students taking neither rhetoric nor literature—the physics students—but we don't know about the overlap between students who are taking rhetoric and those who are taking literature.

Incorrect. If we couldn't infer the some version of this answer in (C), there's no chance we can infer a stronger version here.

Incorrect. We know there are art students who aren't taking literature, but we don't know if any of them are taking it.