Logic: Fork in the road with three men

[Benny]

Originally Posted by The Alexanders

How's that?

Good, but not the best solution.

Something to note is that your first question (which you have to ask 3 times) determines the odd one out, because the random could answer either way. That means after asking question 1 you either know the liar or the truth-teller. If you know the liar you can ask them which leads to city B to get them to tell you which leads to city A. Otherwise if you know the truth-teller, then you just ask them which leads to city A and their answer is correct.

Total number of questions asked = 4

I think this puzzle is very hard, so unless someone posts a better answer before September, I'll post the correct answer and give you half the tokens (250) for this answer.

[JulieA]

Thank you Benny. That's the best I can come up with, so I'll wait for someone else to find a better way.

[Benny]

To get the best answer you have to use some probability and logic theory.

Hi, I'm pretty new at this stuff but i was thinking that you ask all 3 men the same question untill one of them changes the answer in which you can determine which one randomly tells the truth/lies. Then you ask the remaining 2 men a question in which you know the answer to and from there you determin which one tells the truth, and just ask him which city each fork leads to. Is that close ?

[Benny]

That's a good attempt. It would reveal which man was which, assuming that the random answerer will change their answer eventually. However, you cannot make this assumption and it doesn't give you a definite answer for the number of questions you have to ask.

Keep trying

Lets just say i was wearing a blue shirt, i would ask all three 1 at a time "Is my shirt blue, 1 of them has to lie and say no. If the random guy, also said no, I would then know who was telling the truth, since I know the colour of my shirt. Now knowing which is the liar, or which is telling the truth, dependant on the random guy of course, i would ask the liar if the road to the left leads to City A, if he replied no, I would know that it indeed was, as he is the liar. And of course visa versa for the guy telling the truth. I make that 2 questions, what u think?

[Benny]

Originally Posted by design100

I make that 2 questions, what u think?

I make that 4 questions since you ask each of them the first question. This is the same answer that The Alexanders has already posted for this puzzle, so you'll have to do better than that! ;-)

Ok i think i got it, my question would be " are there three people standing in front of me". Which would give me the liar, therefore next question would be pointing to road "A" is this the road to City A, If he answered yes, go with road B, if he answered No. Take that road.

[Benny]

Originally Posted by design100

Ok i think i got it, my question would be " are there three people standing in front of me". Which would give me the liar

How would that give you the liar unless you ask it to all of them and the random answered truthfully? This is still the same as your last answer.

Appologies i messed up there, it would give me either, the truth teller or the liar depending on the random guys answer. I understand that you say this is similar to my last answer, but i feel that this time i am making reference to something that is in the question, rather than assuming that i was wearing a blue shirt. As we know from the question, there are 3 men standing in front of me, and should the random guy say NO, aswell as the Liar, I will know the truth teller, and therefore ask him if road A is the correct road to CityA, if he said yes I would be on my merry way. Should the random guy answer YES, I would then know the Liar, and could ask the same question, depending on his answer YES/NO, I would do the opposite.

Sorry if this isn't right, its the best i got, so will waite for the answer in September.