Prisoner dilemma

Mav · 06-04-2007

You are confined in a prison cell. There are two doors, both of which are unlocked. One leads to freedom, one leads to certain death, but you don't know which is which. Each door is guarded. One guard always tells the truth, one always lies, but again, you don't know which is which.
You are allowed to ask ONE question to identify the door which leads to freedom. You may put your question to either of the guards, bearing in mind that you don't know which one will tell the truth.

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7up · 01-08-2007

It would need to be something without a verbal response...
"Could the guard with the door to freedom please open the door?"
Either that or "Can I have a Big Mac and Fries please?" lol

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picbits · 18-01-2013

"Which door would the other guard say led to certain death ?"
Then pick the opposite door

petlew · 30-08-2007

Better still, stay put in your cell and enjoy the TV, internet, good food and other luxuries and wait until somebody else can't stand the suspense any longer and see what happens.

Experience; is something you gain, just after you needed it most.

When faced with two choices, simply toss a coin. It works not because it settles the question for you. But because in that brief moment while the coin is in the air. You suddenly know what you are hoping for.

artmo · 12-08-2007

Quote from: picbits
"Which door would the other guard say led to certain death ?"
Then pick the opposite door

I think you are on the right lines but surely you would have to ask both guards a question

picbits · 18-01-2013

Nope you'd only have to ask the one guard.
If you asked the guard who always told the truth, you'd get a correct answer - the other guard would lie about which door led to certain death so you'd pick the opposite door.
If you asked the guard who never told the truth, he'd lie about the answer the truthful guard would give hence needing to choose the opposite door again.

artmo · 12-08-2007

.......but you don't know which guard tells the truth and which one doesn't

picbits · 18-01-2013

You don't need to ....

Strat · 14-04-2007

*Strat goes off to watch Labyrinth

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7up · 01-08-2007

Quote from: picbits
You don't need to ....

Yes you do. If you don't know which guard lies then how do you know to pick the opposite door? Likewise if you don't know which guard tells the truth.

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picbits · 18-01-2013

Oops - I actually got it the wrong way round ....
You would pick one of the two guards at random, ask them which door the other guard would say would lead to certain death then pick the door that wasn't mentioned.
door a = death
door b = life
truthful guard would say lying guard would say door b
lying guard would say the truthful guard would say b
so pick the door mentioned and you'd be safe.

kmilburn · 30-07-2007

@Picbits.... You got it wrong before, then made the same mistake again, but at least you got it right in the end...

Ultimately, which door to pick depends on the question asked:
If you ask which door the other guard would say leads to certain death, you pick the door he say.
If you ask which door the other guard would say leads to safety, you pick the other door.
You're effectively getting both guards answer with a single question, and as the true answer is negated by the lie (true & false == false), your guaranteed the answer is always a lie.

journeys · 24-09-2008

Reminds me of the story told of Karl Marx and the two door syndrome. One door represents heaven and the other “the other place”. But he is allowed to have a peek through both doors first.
Through the first door he sees himself being waited upon by a Marilyn Monroe.
He rather like that place, but as he has a choice he chooses to have a peek through the second door he sees himself being waited upon by the same Marilyn Monroe.
He asked why it was the same scene, how can it represents heaven and the “the other place”.
The first door shows the scene of Karl Marx being rewarded.
The second door shows Marilyn Monroe being punished.
(change names to suit audience)
Mind you might have been Groucho! not Karl!

Gabe · 29-10-2008

Three doors, two goats, one car:
Okay, this time imagine you're on a game show, and the host gives you the choice of three doors: behind one door is a car, behind the other two are goats. You pick a door, but the host, who knows what's behind the doors, decides to mess with your mind. He opens one of the other doors, deliberately revealing a goat. He then asks you if you want to stick with your choice or switch. Which do you do, stick, switch, or doesn't it matter?
Answer

ejs · 10-06-2010

That depends on if you want the car or a goat.