One question. One answer. Two guards. Make their truth-telling — or lying — point you to the right door.
by MindYourPuzzle
Two doors. One leads to safety; one to certain death.
Two guards stand watch. One always tells the truth; the other always lies. You don’t know which is which.
You may ask one guard one yes/no question. What do you ask, and how does the answer tell you which door is safe?
① Pick a guard to question
② Your question (what you ask the guard)
③ The guard answers Yes or No. Which answer makes you take the LEFT door?
Don’t know which is the truth-teller — that’s the puzzle. Your single question must work no matter which guard you picked.