Two-door puzzle with one truth-teller and one liar

[ashishsinghal]

There are two doors - one has lots of gold. You want to get gold . There are two guards (one for each door). Both of them know behind which door gold is kept. One guard always says the truth while the other always lies. You do not know who says the truth or who lies.
But the guards know who lies and who speaks truth. You can ask only one question. What would that be?

 

[ashishsinghal]

Please read this before answering.


https://www.physicsforums.com/showthread.php?t=100534

 

[micromass]

That's a classic one

Spoiler

What would the other guard tell you if I asked him "After which door is the gold?"?
Then pick the opposite door...

Here's a nice variants:

There are three doors, and there are three guards: one always speaks the truth, one always lies, and one randomly lies and speaks the truth. Furthermore, the speak in an unknown language, so you won't know what is yes and what is no.
You can ask three questions before deciding which door leads to the gold. Which questions would you ask?

 

[disregardthat]

There are three doors, and there are three guards: one always speaks the truth, one always lies, and one randomly lies and speaks the truth. Furthermore, the speak in an unknown language, so you won't know what is yes and what is no.
You can ask three questions before deciding which door leads to the gold. Which questions would you ask?

This is nearly an impossible puzzle, it's the hardest logic puzzle ever!