This is a good puzzle - except I can't solve it!

[Herremann the Wise]

Hi everyone,
I love puzzles but I am so hopeless at them. The following would be excellent in a game but for the life of me I can't do it (calling all Hypersmurf's to smurf their way through this smurfy puzzle please ).

I was tutoring one of my maths students yesterday and he laid this one on me:

"There are two guards in a corridor, one guarding a doorway to heaven, the other guarding a doorway to hell. One of the guards will always tell the truth but the other will always lie.
By asking a single question that both the guards answer, find the doorway to heaven."

I have a bad feeling this is really simple but for the life of me I have no idea - and I like to call myself a maths tutor.
It seems like it would be a good in game puzzle if you had two doors in a dungeon guarded by a pair of demonic fey or something and one lead the way you wanted but the other lead to a terrible trap.

Thanks everyone for helping me out.

Best Regards
Herremann the Wise

 

[FireLance]

Spoiler

Ask each guard, "If I ask the other guard which is the doorway to heaven, what will he say?"

The truthful guard will point to the doorway to hell because that is what the lying guard will say.

The lying guard will also point to the doorway to hell because the truthful guard will point to the other door.

Alternatively (more convoluted), point to any door and ask, "If I asked you this was the doorway to heaven, what would you say?"

The truthful guard will say either "Yes" or "No", truthfully.

The lying guard will also say "Yes" or "No" truthfully, because he would normally lie, and would lie about his lying response when he answers the question.

 

[Jolly Giant]

Ah, this is a golden oldie! Ask either guard (doesn't matter which!): "If I asked the other guard, which door would he tell me led to heaven?"

Whatever door the guard then indicates leads to hell, the other one leads to heaven.

 

[janta]

Wasn't this puzzle used in the movie Labyrinth? That's what I thought of when I saw the OP. If you've got fans of that movie in your campaign, you might not want to use this puzzle....

--Janta

 

[Richards]

They also used this puzzle on an episode of "Doctor Who" -- it was in "The Pyramids of Mars," I believe.

Johnathan

 

[Asmor]

This an a very common puzzle that most people know about, but I've never heard FireLance's second answer. I like that one a lot more, very cool!

 

[Thanee]

"There are two guards in a corridor, one guarding a doorway to heaven, the other guarding a doorway to hell. One of the guards will always tell the truth but the other will always lie.
By asking a single question that both the guards answer, find the doorway to heaven."

If you cannot solve this (which is really not so hard), you should not even look at the advanced version of this puzzle.

Three Gods - A, B and C - are called, in some order, True, False and Random. True always speaks truly, False always speaks falsely, but whether Random speaks truly or falsely is a completely random matter. Your task is to determine the identities of A, B and C by asking three yes-no questions; each question must be put to exactly one God. The Gods understand English, but will answer all questions in their own language, in which the words for 'yes' and 'no' are 'da' and 'ja', in some order. You do not know which word means which.



Bye
Thanee

 

[Thanee]

This an a very common puzzle that most people know about, but I've never heard FireLance's second answer. I like that one a lot more, very cool!

Yep, very clever.

Bye
Thanee

 

[DonaldRumsfeldsTofu]

Three Gods - A, B and C - are called, in some order, True, False and Random. True always speaks truly, False always speaks falsely, but whether Random speaks truly or falsely is a completely random matter. Your task is to determine the identities of A, B and C by asking three yes-no questions; each question must be put to exactly one God. The Gods understand English, but will answer all questions in their own language, in which the words for 'yes' and 'no' are 'da' and 'ja', in some order. You do not know which word means which.

My head just exploded

 

[Xath]

Wasn't this puzzle used in the movie Labyrinth? That's what I thought of when I saw the OP. If you've got fans of that movie in your campaign, you might not want to use this puzzle....

--Janta

That was the first thing I thought when I saw this. Definitely be careful using this riddle, as many people have seen that movie.