17 Jun 15
The answer is you ask both of them this question - If I was to ask the other person which one will tell the truth, what would they say?
If you are asking the lier he will lie and say its him. If you ask the one that tells the truth he will know that the other one will always lie and so he will point to the other person. So that identifies the lier as both will have indicated the same person.
28 Jun 15
Originally posted by Julian DaviesCorrect answer - ask Mr Left the following: "If I asked Mr Right which way to go, what would he say?"
Point to one of them and ask the other "Would he call you a liar?" If the answer is no the one you are asking is the liar. If yes the one you are pointing at is the liar. Sorted with one question.
Let us assume North is the correct direction.
If Left is the liar, then Right would say North, but Left would change the answer to South.
If Left is the truth teller, Right would say South, and Left would correctly report the answer as South.
Either way, you get the wrong answer, and go the other way.
21 Jul 15
Originally posted by Duncan ClarkeThis is a bit of a trick question.
You face 2 people. One always tells the truth, and 1 is a liar.
You can ask 1 question, the same to each.
How can you discover which one is the liar?
The question that you must ask is "are you a liar?"
The person who always tells the truth, MUST answer "no"
The person who is a liar MAY answer "yes". If he does, you have identified the liar. Otherwise, you can't.