LSAT (Law School Admission Test)Analytical ReasoningHard
A librarian is arranging seven new books—F, G, H, I, J, K, L—on a single shelf from left to right. The arrangement must conform to the following rules: 1. Book F must be placed immediately to the left of Book H. 2. Book G must be placed somewhere to the right of Book J. 3. Book I cannot be placed next to Book K. 4. Book L must be placed in either the first or the seventh position. 5. If Book F is in the third position, then Book J must be in the first position. If Book K is placed in the second position, which of the following books CANNOT be placed in the fourth position?
- AG
- BF
- CJ
- DL
Show answer & explanationAnswer & explanation
Correct answer: D. L
If K is in the second position, then I cannot be in the first or third position (rule 3). L must be in the first or seventh position (rule 4). Since K is in second, L cannot be first. So L must be seventh. Therefore, L cannot be in the fourth position.
Why the other options are wrong
- A. If G is in the fourth position, K is second. I is not first or third. L is seventh. J is somewhere left of G. This is possible (e.g., J, K, I, G, F, H, L).
- B. If F is in the fourth position, then H is in the fifth (rule 1). K is second, I is not first or third. L is seventh. J is somewhere left of G. This is possible (e.g., J, K, I, F, H, G, L).
- C. If J is in the fourth position, K is second. I is not first or third. L is seventh. G is right of J. This is possible (e.g., F, K, H, J, I, G, L).
Inference from Constraints
Deducing new, implicit rules or facts by combining existing explicit constraints.
- Often involves combining two or more rules.
- Results in a 'must be true' or 'cannot be true' conclusion.
- Crucial for advanced analytical reasoning.
Memory trick: Logic's Path Ensures Certain Truths.