Which Way?
You're off to see the wizard ... the wonderful wizard of ... uh ...ok ... forget that. You are on a journey and come to a fork in the road. Standing there at the fork are two wizardly looking gentlemen ... ok .. they may not be gentlemen, but they are standing there. A truthful sign is on a post mounted in the ground next to the two men. The sign reads:
ONE OF US IS A TRUTH TELLER ... THE OTHER IS A LIAR
-------- Travelers may ask one of us ... one question ---------
What question do you ask, to obtain the correct information concerning the correct road upon which to continue your journey?
ONE OF US IS A TRUTH TELLER ... THE OTHER IS A LIAR
-------- Travelers may ask one of us ... one question ---------
What question do you ask, to obtain the correct information concerning the correct road upon which to continue your journey?
posted by Zaux at
4:22 PM
13 Comments:
you ask them both: what would the other person say is the correct road?
the truthful person would tell you that the liar would tell you the wrong way.
the liar will tell you the opposite of what the truthful guy would say which also ends up being the wrong way.
so now that both of them are pointing in the wrong direction, you take the other road and keep your appointment with the wizard (fraud!)
hi Jayson ...
read the sign agaain ...
my bad, well in that case, if you ask either one that question they'll still be pointing in the wrong direction without a doubt. so you can get the hell out of there as fast as you can
Yeah, Ask one of them what way the other would say.
... problem is there's still a fork in the road and a decision must made
Hi Ragknot ... good answer ... will you elaborate as to how the correct road is selected?
sure, I was going to add,
Then go the other way.
The question would be "Which way would the other say?
The truth teller will tell you the lie the liar would tell you.
The Liar would tell you the wrong way, (the opposite of what was the truth teller would say)
Jayson's answer sounds good to me
you ask one of then "if i asked the other one which road is correct,what would he say"
in any case,you will get a lie.
Actually Jayson said mostly what I was going to say, I was just agreeing with him.
yep ...Jayson wins the grand prize of ... oh wait ... he gets to continue on the right road to the wizard
Looks like we are not giving details because we don't know the details.
Suppose we are going to A, but the signs say "This way to N, and that way to S. And we don't know which is also the way that also includes A.
So we ask one of the men, "Which way would the other guys say, takes me to A?"
If the true path is toward N, either guy would tell you toward S.
The liar would say the truth teller would say S.
The truth teller would say the liar would say S.
Then you know N is the right way.
A very similar puzzle was used to very good effect in the movie "Labryinth".
http://www.youtube.com/watch?v=2dgmgub8mHw
"One of them leads to the castle and the other one leads to ... (dum dum dum dum) certain death!"
Ask one of the men what the other man would answer to the question "Is the left road the correct road?" You assume the info given is false and act accordingly.
If the one you ask is the liar, he will incorrectly give you the truthful man's answer. If the man you ask is the truth teller, he will correctly give you the liar's wrong answer.
Alternate possiblity:
You can ask one of them, "If I had asked you which road was the correct road ten minutes ago, what would you have said?" Regardless of which one you ask that question, the answer will be the correct road.
And that, my friends, is the published solution... ;)
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