This puzzle is always presented as difficult, but why not just ask a known? If your eyes are brown just ask “Are my eyes brown?” You’d immediately know which one lies or tells the truth.
Because there are two doors and only one question. If you ask a known question unrelated to the door you find out who the liar is but lose your opportunity to ask them which is the correct door.
The difficulty comes from only being able to ask one question. It’s very easy to figure out the liar, but it’s much more difficult to figure out the liar and the correct door in the same question
In fact, the lying guard is a red herring. You get one question, and need one piece of info: the door. The canonical question doesn’t tell you which guard lies, nor do you care to find out.
This puzzle is always presented as difficult, but why not just ask a known? If your eyes are brown just ask “Are my eyes brown?” You’d immediately know which one lies or tells the truth.
E: I missed the limit of one question.
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Because there are two doors and only one question. If you ask a known question unrelated to the door you find out who the liar is but lose your opportunity to ask them which is the correct door.
The difficulty comes from only being able to ask one question. It’s very easy to figure out the liar, but it’s much more difficult to figure out the liar and the correct door in the same question
In fact, the lying guard is a red herring. You get one question, and need one piece of info: the door. The canonical question doesn’t tell you which guard lies, nor do you care to find out.
Knowing who lies and who tells the truth doesn’t tell you which door leads to the prize and which to death.