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#250323 - Mon Nov 29 2004 09:46 PM Brainteaser
Neume Offline
Explorer

Registered: Thu Sep 30 2004
Posts: 50
Loc: Indiana, USA
Here's a riddle for you:
You are standing in a room with 2 doors. You know that one leads to Heaven, and the other to Hell, but you do not know which door is which. There is no other way out, and once you open a door, you must enter it. Between the two doors are two computers: one always lies, and the other always tells the truth. You do not know which computer is which.
The challenge? You can ask one question of one computer to determine which door leads where. What question will give you that answer beyond the shadow of a doubt?
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All that is gold does not glitter, Not all those who wander are lost.

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#250324 - Sat Dec 04 2004 12:04 PM Re: Brainteaser
Neume Offline
Explorer

Registered: Thu Sep 30 2004
Posts: 50
Loc: Indiana, USA
C'mon, guys! Somebody give it a shot.
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All that is gold does not glitter, Not all those who wander are lost.

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#250325 - Sat Dec 04 2004 05:18 PM Re: Brainteaser
Gatsby722 Offline
Pure Diamond

Registered: Fri May 18 2001
Posts: 123698
Loc: Canton
Ohio USA    
I am SO sure this is not the right answer but I'd skip the computers altogether. I'd just feel the doors and if one was hot I'd go to the other one!

But now that I'm thinking it through, I might ask one of the machines: "If I want to go to Heaven should I enter the door on the right or in the middle?" If I'm asking the liar computer and it replies "right" then I'd know to go to the left one since there is no middle door. But, hmmm..., that wouldn't quite work since if it says "middle" it might be lying about the right door, too. Puzzling!
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"The best teacher is not the one who knows most but the one who is most capable of reducing knowledge to that simple compound of the obvious and wonderful." ... H. L. Mencken


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#250326 - Sat Dec 04 2004 05:20 PM Re: Brainteaser
Gatsby722 Offline
Pure Diamond

Registered: Fri May 18 2001
Posts: 123698
Loc: Canton
Ohio USA    
I think I confused even myself on that reply... !
_________________________
"The best teacher is not the one who knows most but the one who is most capable of reducing knowledge to that simple compound of the obvious and wonderful." ... H. L. Mencken


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#250327 - Sun Dec 05 2004 04:44 AM Re: Brainteaser
TabbyTom Offline
Moderator

Registered: Wed Oct 17 2001
Posts: 8451
Loc: Hastings Sussex England UK    
I think you ask one of the computers something like “If I asked you ‘Does the door on the right lead into Heaven?’, would you say ‘Yes’?”

Suppose the right-hand door really does lead into Heaven. In that case, the truth-teller naturally says “Yes.” If the liar had been asked ”Does the right-hand door lead to Heaven?”, it would have said “No”: so it must also answer you question with “Yes” in order to lie.

If the right-hand door goes to Hell, the truth-teller says “No.” If the liar had been asked simply “Does the right-hand door go to Heaven?”, it would have said “Yes”: therefore it must also say “No” to your question.

So, no matter which computer you ask, you can safely use the right-hand door if the answer is “Yes” and the left-hand door if it’s “No” – or the other way round, of course, if you think you’ll prefer the company in Hell.
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#250328 - Sun Dec 05 2004 08:52 PM Re: Brainteaser
craigal Offline
Explorer

Registered: Sun Apr 16 2000
Posts: 82
Loc: Sydney NSW Australia         
There is another way

Let call the computers Computer1 and Computer2

Ask computer1 this question

"If I was to ask Computer2 which door lead to heaven what would the answer be?"

You then would take the door opposite to the answer.

If computer1 is the truthful one then computer2 will lie about which door goes to heavan.

If the computer1 is a liar then it will answer the opoosite door to which the truthful door would answer.

cheers

Craig

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#250329 - Thu Dec 09 2004 09:32 AM Re: Brainteaser
Neume Offline
Explorer

Registered: Thu Sep 30 2004
Posts: 50
Loc: Indiana, USA
Congratulations to craigal, He got it! Thanks for participating, everyone.
_________________________
All that is gold does not glitter, Not all those who wander are lost.

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