Logical Puzzles made clear.
Turn prose into a small set of constraints. A neat grid and a deliberate test of alternatives usually beat trying to hold every clue in memory.
Key concepts in Logical Puzzles
Assignment puzzles
Match people to one-to-one attributes such as days, floors or colours. Mark confirmed and excluded cells.
Ordering puzzles
Translate “before”, “after” and “immediately before” into different constraints.
Unique solution
A complete arrangement is valid only if it satisfies every clue. Several valid arrangements mean some answers are not determined.
Conditional clues
“If P then Q” does not imply “if Q then P”. Apply the direction actually stated.
Constraint grid: unique colours
| Person | Red | Blue | Green |
|---|---|---|---|
| A | Excluded | Excluded | Yes |
| B | Excluded | Yes | Used by A |
| C | Yes | Used by B | Used by A |
A reliable solving method
- List the entities, available positions and whether repeats are allowed.
- Place the strongest fixed clue first.
- Propagate exclusions after each placement.
- Branch only when necessary, and reject any branch that breaks a clue.
Step-by-step solved examples
Ana, Bala and Chen present on Monday, Tuesday and Wednesday, one each. Ana is before Bala; Chen is not Wednesday. Who presents Wednesday?
- Bala cannot be Monday because Ana must be earlier.
- If Bala were Tuesday, Ana would be Monday and Chen Wednesday, contradicting the clue.
- Therefore Bala is Wednesday; Ana and Chen may exchange Monday and Tuesday.
Three people A,B,C live on floors 1,2,3, one each. A is above B and C is on floor 2.
- Only floors 1 and 3 remain for A and B.
- A must have the higher remaining floor.
- A is on 3 and B on 1.
A,B,C wear red, blue and green, one each. A is not red or blue; B is not red.
- A must wear green.
- B cannot use red or the already used green, so B wears blue.
- C wears red.
Logical Puzzles: practice questions
Choose one answer before opening the explanation. Write down your reasoning as well as the option; a correct guess is different from a method you can repeat.
A before B, B before C, in a 3-person order. Who is first?
Show answer and explanation — question 1
Answer A: A
The chain is A→B→C.
A,B,C occupy floors 1–3. C is on 3, A above B. A’s floor?
Show answer and explanation — question 2
Answer B: 2
A and B occupy 1 and 2, with A higher.
Three unique colours. A red, B not blue. C’s colour?
Show answer and explanation — question 3
Answer C: Blue
B must be green, leaving blue for C.
A is before B among four people. Must A be first?
Show answer and explanation — question 4
Answer B: No
Others may stand before A while A remains before B.
A immediately precedes B. Which order violates the clue?
Show answer and explanation — question 5
Answer C: A C B
C between A and B breaks immediate adjacency.
Two different arrangements satisfy all clues. What can be concluded?
Show answer and explanation — question 6
Answer D: Only facts shared by all valid arrangements are certain
A definite answer must hold across every permitted arrangement.
Frequently asked questions
Should I use trial and error?
Use controlled branching after placing definite clues; record each assumption so you can undo it.
What if a question asks “could be true”?
You need one valid arrangement supporting it. “Must be true” requires it in every valid arrangement.
List the entities, available positions and whether repeats are allowed. Branch only when necessary, and reject any branch that breaks a clue.