Halp!

[ArcticChicken]

So, in my math class this week we are doing logic.

As an extra credit problem, my teacher asked us when you are faced with two paths, and one leads to treasure and the other to certain death, and there are two guards, and you know that one of them always lies, and one of them always tells the truth, logically prove that "If I were to ask the other person which way leads to the treasure, what would he say?" is the correct question to ask.

I know why it is the correct question, but I do not know where to start on proving it. Any ideas?

[Whiskey]

LOL he rephrased one of the oldest riddles ever.

You ask, "Which way would your companion say is the correct expression?". The liar would lie tell you that the truthful man would say a=c. The truthful man would tell the truth and say that the liar would tell you a=c. They both point say a=c, so then a=b is the correct expression.

Usually its about heaven and hell though.

edit: i dont even know if i answered your question, i hate this riddle. I was just talking about it yesterday actually. :|

[AriGriffin]

"The trick is not to find out which one is lying and which one is telling the truth but to find out how to get them both to give the same sort of answer. If you ask one guard Would he tell me this door leads to the castle? Whatever answer they give you is the opposite of the truth. You're either asking a truthful person what a liar would say (So you get a lie answer, you're truthfully told what the liar would say.). Or you ask a liar what the truthful person would say (so get the lie answer because that's who you're talking to, lie by default)." from http://www.imdb.com/title/tt0091369/faq

[ArcticChicken]

I know why it's the right question, I just don't know how to prove it mathematically.

[terakhan]

All math is logical, but not all logic is mathematical. Just explain the solution in detail and you should be good. If he insists on math from it, he is a moron anyway.

[TheMike]

it is not in itself subject to a "formulaic answer" it is the basis for logical reasoning.

[Andara Bledin]

Actually, this one is easy, and I figured it out before they got to the answer while reading a comic adaptation of Labyrinth, which is the first place I encountered it.

You just work through the details of both possible scenarios, and you should be good.

^-.-^