OK, the puzzle that Sparkle sets is fairly old and traditional (and potentially extremely funny - this comic had me laughing for ages when I first saw it, and still cracks me up), so here's a slightly harder version. Not much harder, but a little.

Same set up, except there are multiple guards. Some guards always tell the truth, some always lie. You don't know which are which and you don't know how many there are of each. The guards also don't know which each of the others are, although obviously they still know whether they themselves tell the truth or lie. You still only get one question to one random guard to determine which of the two doors leads to freedom.

What question do you ask, and how do you use the information?

I always hated that mind puzzle. but lately I've seen some really good answers that doesn't require a lot of thinking.

All you do is injury one or both of them, I think neopets had it one time that you poke the guy in the eye with a stick, If he said you where poking him he was telling the truth, if he denied that he was being poked he was lying.

I think I also heard one more recently where they shot the guy. yea, trying lying though that. "I haven't been shot, not at all" you didn't ask a question. but you know know who is lying.


Actually I have a book on False logic puzzles, I don't know why I bought it. I hate them. after trying to do one or two you realize there is no earthly way you would ever be in a situation such as that. Sort of like ethic/moral questions isn't it?

RA, were you thinking of this:
[www.giantitp.com]

As is so often the case violence beats logic. GO Violence!

Or more simply: If I were to ask you which way was the right way, what would you say?

I have to thank you! I had forgotten who showed me the link to that comic! (I'm hooked now, but he's on vacation, bummer)but it was the second time I've seen it solved like that, Neopets did indeed have a similer solution. (poking instead of arrowing but nearly the same)

Rookee... if you poke someone and then ask them whether they've been poked... that's it, you know which guard is lying, but that doesn't tell you which door to go through.

An answer would be...
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"Which door would a guard who answers the opposite to yourself tell me is the right one?" Again, whether you have a truth-teller or a lie-teller, you've filtered the answer through both responses, so you know you're geting a lie.
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Other answers may be available.

Rob

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That statement is either so deep it would take a lifetime to fully comprehend every particle of its meaning, or it is a load of absolute tosh. Which is it, I wonder?
Terry Pratchett, Hogfather

the idea behind the Poking/violence, is that the person (whether lying or not) will be bothered enough to say something without being asked. Then you can ask. Or in the case of the comic shown above have them each tell you which way to go first and then hurt one of them.

but of you want to follow the rules go ahead.... ;)

I'm a trained mathematician.... logic and rules are important to me. If people don't take things like this seriously it could lead to the end of the world as we know it!!!

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That statement is either so deep it would take a lifetime to fully comprehend every particle of its meaning, or it is a load of absolute tosh. Which is it, I wonder?
Terry Pratchett, Hogfather

I prefer Haley's solution. Darned logic puzzles!!! Anyway, I have a math major brother who takes care of them for me (in between playing games of Car Wars)...

Robc,

You are a mathematician.

I'm an Aussie. I'd just say 'Bugger it', and go and have a drink.