Originally Posted by ChrisNukemYJ
You come to a junction in the road.
One road leads to the City of Truth, where everyone is always honest.
The other road leads to the City of Lies, where everyone always lies,
but you don't know which is which. There is also a man at the junction.
You can ask him one and only one question to find out where the City of Truth is.
What is the question and why?
The question to ask is "Which road would you not take to the city of truth? "
But the problem with this is that there is only one person there so you will still not know which road because that person might be telling the truth or they might be lying.
There should be two people there, one from the city of truth and one from the city of lies. Now the question would be for either one of them and ghat would be "If I asked the other person which road to take to the city of truth, which road would they say?
The reason for this question is no matter who you asked, you would do the opposite. Because the lier would say or point to the road to the city of lies and the person from the city of truth would say or point to the road to the city of lies also.