Knights Knaves Spies
1. Problem 28:
A says “C is the knave,” B says “A is the knight,” C says “I am the spy.”
- Assign roles: one knight (always truth), one knave (always lie), one spy (can lie or truth).
- If A is knight (truth): then C is knave (true), B says A is knight (true), C says “I am the spy” (false, since C is knave). Consistent.
- If A is knave (lie): then C is not knave, contradicts B’s statement if B is knight or spy.
- If A is spy: more complex, but checking shows no consistent assignment.
Conclusion: Unique solution: A = knight, B = spy, C = knave.
2. Problem 29:
A says “I am the knight,” B says “I am the knave,” C says “B is the knight.”
- B says “I am the knave” is a paradox if B is knight or knave.
- If B is knave (lying), statement false, consistent.
- A says “I am the knight,” if true, A is knight.
- C says “B is the knight,” false since B is knave.
Conclusion: Unique solution: A = knight, B = knave, C = spy.
3. Problem 30:
A says “I am the knave,” B says “I am the knave,” C says “I am the knave.”
- Knights cannot say they are knaves (would be false).
- Knaves cannot say they are knaves (would be true).
- Spies can say anything.
- All three claim knave, impossible for all three.
Conclusion: No solution.
4. Problem 31:
A says “I am the knight,” B says “A is telling the truth,” C says “I am the spy.”
- If A is knight, A’s statement true.
- B says “A is telling the truth,” true if B is knight or spy telling truth.
- C says “I am the spy,” if true, C is spy.
Check assignments:
- A knight, B spy (truth), C knave (lying) contradicts C’s statement.
- A knight, B knight, C spy consistent.
Conclusion: Unique solution: A = knight, B = knave, C = spy.
5. Problem 32:
A says “I am the knight,” B says “A is not the knave,” C says “B is not the knave.”
- If A is knight, A’s statement true.
- B says “A is not the knave,” true.
- C says “B is not the knave,” true.
If both B and C say true statements, both cannot be knaves.
Try A knight, B spy, C knave:
- B’s statement true (spy can tell truth), C’s statement false (knave lying).
Conclusion: Unique solution: A = knight, B = spy, C = knave.
6. Problem 33:
A says “I am the knight,” B says “I am the knight,” C says “I am the knight.”
- Only one knight.
- If A is knight, B and C lying.
- B and C say “I am the knight,” false.
Conclusion: Unique solution: A = knight, B = knave, C = spy.
7. Problem 34:
A says “I am not the spy,” B says “I am not the spy,” C says “A is the spy.”
- If A is spy, A’s statement false.
- C says “A is the spy,” true.
- B says “I am not the spy,” true.
Try A spy, B knight, C knave:
- C lying contradicts C’s statement.
Try A knave, B spy, C knight:
- A lying about not being spy (true, since A knave), C telling truth.
Conclusion: Two possible solutions:
- A = spy, B = knight, C = knave
- A = knave, B = spy, C = knight
8. Problem 35:
A says “I am not the spy,” B says “I am not the spy,” C says “I am not the spy.”
- Only one spy.
- Two people claim not spy, one must be lying.
Try A knight, B knave, C spy:
- B lying about not being spy (true, since B knave), consistent.
Try A knave, B knight, C spy:
- A lying, B truth, consistent.
Try A knave, B spy, C knight:
- A lying, B truth, consistent.
Conclusion: Multiple solutions:
- A knight, B knave, C spy
- A knave, B knight, C spy
- A knave, B spy, C knight
Final answers summarized.