LSAT (Law School Admission Test)Analytical ReasoningMedium
A librarian is arranging six new books—Fiction (F), History (H), Memoir (M), Poetry (P), Science (S), and Travel (T)—on a single shelf from left to right, numbered 1 to 6. The arrangement must conform to the following conditions: 1. The Science book must be placed immediately to the left of the Travel book. 2. The History book must be placed in an even-numbered position. 3. The Poetry book cannot be placed next to the Memoir book. 4. If the Fiction book is placed in position 3, then the Science book must be placed in position 4. If the Memoir book is placed in position 5, which of the following is a complete and accurate list of positions in which the Poetry book could be placed?
- A1, 2
- B1, 2, 3
- C2, 3, 4
- D1, 3, 4
Show answer & explanationAnswer & explanation
Correct answer: B. 1, 2, 3
If M is at 5, P cannot be at 4 or 6. This leaves 1, 2, 3. H must be at an even position (2, 4, 6). Since M is at 5, the S-T block must be placed. If S-T is at 1-2, then H could be at 4 or 6. If S-T is at 3-4, then H could be at 2 or 6. If S-T is at 4-5, this is not possible as M is at 5. So, S-T can be 1-2 or 3-4. This leaves positions for H and P. If P is placed at 1, 2, or 3, it always satisfies the rules.
Why the other options are wrong
- A. Incomplete; P could also be at 3.
- C. Incorrect; P cannot be at 4 (next to M).
- D. Incorrect; P cannot be at 4 (next to M).
Exclusion by Proximity
A type of negative constraint where two elements cannot be placed immediately adjacent to each other. This creates 'forbidden zones' around one of the elements.
- Defines spaces where an element cannot be placed.
- Often combined with fixed positions to narrow possibilities.
- Can apply to elements on either side of a given element.
Memory trick: No hand-holding allowed for these two.