Two guards, two doors
There are two doors: one safe, one fatal. Two guards stand watch - one always lies, one always tells the truth - but you don't know which is which. You may ask one guard a single yes/no question. What do you ask to find the safe door?
Show hints (2)+
- Force the lie and the truth to compose.
- Ask about what the other guard would say, then invert.
Answer
This is an open-ended question - work through it and compare your reasoning.
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Asked at: Probability & Market-Making, EV & Betting Games