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by polishdude20 on December 18th, 2006

polishdude20

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Riddle:A man is sentenced to death but he gets to choose the life door or the death door. there are only two doors and they look exactly the same. there are two guards, one tells the truth always and one always lies.you can ask 1 question what is it?

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Answers. 30 helpful answers below.

  • by Anonymous on January 14th, 2007

    Anonymous

      I ask one of the guards the following question:  “If I were to ask the other guard, which exit leads to escape, what would he tell me?”  Whichever exit is indicated by the answer that I receive, I then take the other exit.

      It does not matter whether I ask the guard that tells the truth, or the guard that lies.  I'll get the same answer either way.

      Let us suppose that we recognize both of the guards.  One guard is ex-President Bill Clinton, who we know is totally incapable of ever telling the truth about any subject.  The other is George Washington, who “cannot tell a lie”.

      Now let us suppose that exit A leads to escape, and exit B leads to certain death.

      If I pose the above question to Washington, then he knows that Clinton would lie to me and advise me to take exit B, so that is what Washington would tell me.

      If I pose that question to Clinton, then Clinton knows that Washington would truthfully advise me to take exit A; so Clinton will lie to me and tell me that Washington would advise me to take exit B.

      Either way I get the same answer.  From Washington, a truthful account of the lie that Clinton would tell, or else from Clinton, a lie about the truth that Washington would tell.  Either way, I get an answer that I know is wrong, so I would do the opposite of what it indicates.

    -------------
    [Added c. 14 January 2007, 06:30 PST]

      I don't see how I can explain it any more clearly than I did above, but it seems that several people just don't get it.  Let me see if more detail will help.

      The riddle presumes, of course, that you have no way of knowing which guard tells the truth, and which guard lies.  In the above examples, I assigned the guard roles to a known famous truth-teller and a known famous liar, so that I could show the dynamics.

      Let's stick with all the above assumptions.  The exit to freedom is A, and the exit to death is B.  George Washington will tell you the truth, and Bill Clinton will tell you a lie.

      What happens if you ask either one directly, which door leads to freedom?

      Washington will tell you the truth.  He will tell you that door A leads to freedom.  If you take his advice, you will escape.

      Clinton will lie to you.  He will tell you that door B leads to freedom.  If you take his advice, you will die.

      Now, as the riddle stipulates that you do not know who is the liar, and who will tell the truth; you can't get a useful answer by asking the question directly.  You'll either be told that door A is the one that leads to freedom, or else you'll be told that door B leads to freedom.  Without knowing whether you got that answer from the liar or the truth-teller, you cannot know whether to do as advised, or to take the other door.

      Hence the more complex question:  “If I were to ask the other guard, which exit leads to escape, what would he tell me?”

      Now, you're not directly asking which door to take.  You're asking one guard to tell you what the other guard would tell you.

      Washington knows that if asked directly, Clinton would lie, so Washington would truthfully tell you that Clinton would say that door B leads to freedom.  Of course, this is the wrong answer; as door B is the one that leads to death.

      Clinton knows that if asked directly, Washington would tell you to take door A.  But Clinton is a liar, so he will tell you that Washington would advise you to take door B.  Again, you get the wrong answer.

      Either way, you get an answer that is wrong.  You either get from Washington a truthful account of the lie that Clinton would tell you, or else you get from Clinton a lie about the truth that Washington would tell you.  Either way, you need to to the opposite of what the answer you get indicates.

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  • by scubabob on January 14th, 2007

    scubabob

    Just go up to one of them and ask " If I were to ask your buddy over there, which is the safe way out,what would he tell me?
    Go out the door that he indicates. You'll live.

    Edit For BB, here's the links, go nuts
    http://www.cut-the-knot.org/impossible/brothers.shtml
    http://www.woodlands-junior.kent.sch.uk/fun.html
    Take the -5 off.

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  • by Journo on January 14th, 2007

    Journo

    I would ask each guard, "Which exit would the other guard tell me is the escape from this mine?"
    Both will point to the safe exit.

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  • by EL1 2 on December 18th, 2006

    EL1 2

    Which door would the other guard say that (pointing at one door) is? Then I do the door he says is death.

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  • by - retroglide - on January 26th, 2007

    - retroglide -

    "If I were to ask the other guard, which door would he say leads to freedom?" You would then select the door opposite to the one he picked.

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  • by Firebrand on January 14th, 2007

    Firebrand

    Ask both guards the way out they will both tell you the same way.Take it one is telling the truth

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  • by Wide Awake @ has closing date woo hoo on July 9th, 2009

    Wide Awake @ has closing date woo hoo

    You ask either guard, "If I asked the other guard which door leads to heaven, what would they say?" Then take the other door. There is only one question needed, which can be asked of either guard.

    This sets up a double negative or double positive, and always leads you to the right answer.

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  • by RFlagg on January 26th, 2007

    RFlagg

    I just pick a door at random without asking either gaurd anything.
    That's just the way I operate.

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  • by spazmojack on December 18th, 2006

    spazmojack

    i would ask one of the guards how many doors there are. easy way of finding out which one is the liar and which isn't. then i would blindly assume that the one who is the truth telling guard is guarding the doorway to life and walk on through!

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  • by Wide Awake @ has closing date woo hoo on February 20th, 2009

    Wide Awake @ has closing date woo hoo

    You ask either one, "If I asked the other robot which door to take to get to life, what would they say?" Then take the other door if you want life.

    You have to set up double positive/double negative. It's a very basic riddle that has been asked here dozens of times.

    Let's say Robot A is the truth teller, and Door 1 is the door to life.
    When you ask robot A which door to take, A truthfully says that B would say "Door 2." Therefore you take the other door to save your life.
    When you ask B which door to take, B lies, saying that A would say "Door 2." Therefore you take the other door to save your life.

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  • by VOD on January 26th, 2007

    VOD

    "Does the other guard lie?"

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  • by sweaver9 on January 26th, 2007

    sweaver9

    I would as who ever is guarding the door if they would go with me.

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  • by Anonymous on January 14th, 2007

    Anonymous

      I've thought of an alternative solution.

      Ask this question, of either guard:  “If I were to ask you which door leads to freedom, what would you tell me?”.

      Here, you're not directly asking which door leads to freedom; you're asking what door the guard would say leads to freedom.

      If you ask the truthful guard, he will give you the correct answer.

      If you ask the liar, then he will give you the correct answer (assuming he correctly parses the question, and doesn't just treat it as “Which door leads to freedom?”?).

      This depends on the liar to engage in the sort of pedantic strict interpetation that I often do.  I'm not sure I would ever stake my life on such an assumption, but assuming we could trust it, here is why it would work…

      If you directly ask the liar which door leads to freedom, he will, of course, lie to you, and tell you the door that leads to death.  But that's not what you're asking.  You're asking him what door he would say leads to freeedom, were you to simply ask the direct question.  Since the direct answer would be the wrong door, he will lie about that answer, and the lie that he tells you will indicate the correct door.  This is similar to the logic that ScubaBob was trying unsuccessfully to argue earlier; wherein you get the liar tell a lie about a lie, with the two lies cancelling each other out.

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  • by nurse7263 on January 14th, 2007

    nurse7263

    I'd probably just run headfirst into the wall and kill myself hahahahah

    This question sounds like my discrete math class, and let me tell ya, I never was much good at that!

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  • by staffie on January 14th, 2007

    staffie

    which one of you is lying ? lol
    i dont know really

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  • by jenel615 on July 31st, 2009

    jenel615

    Truthful guard, which door is life?

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  • by rhodza on July 31st, 2009

    rhodza

    where is God?

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  • by Donny on April 15th, 2009

    Donny

    ask one of them if thay are aboule to tell a lie
    if its the one hum tells the truth he will say yes but he is not allowed.
    if its the one hum tells lies he will say no thin ask the other were the door that leeds to life if if its the truthfull one he will give you the right door and vis versa with the one hum lies.

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  • by lamaman on December 18th, 2006

    lamaman

    that depends which gaurd told him that there is a life door and a death door.

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  • by unwantedguilt on May 23rd, 2007

    unwantedguilt

    this specific example is actually a very old logic problem. you ask what the other would say, simply because you do the opposite. the clinton and washington example is cute.. although i did support big bill.

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  • by RockAngel on January 14th, 2007

    RockAngel

    Since one of the beings cannot tell the truth of which would be the devil, I would have to ask just once to either, Do you serve the Lord in heaven who sent His son to earth? It is Faith that leads you out.

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  • by Davecom3 on December 11th, 2011

    Davecom3

    I'd ask one guard, "Which of these two doors would you say is the life door?" Forget the other guy, he doesn't even need to be here.

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  • by Davecom3 on December 11th, 2011

    Davecom3

    Which door would you say is the life door?

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  • by Lora Dee Corr on May 23rd, 2007

    Lora Dee Corr

    I'd ask either guard to walk through either door. If he dies then go through the other!

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  • by Ash on January 6th, 2008

    Ash

    this is the proper answer.

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  • by john pennington on April 17th, 2009

    john pennington

    "Pretend i am your mother. in order to save my life, tell me the truth, is this the real life door"?

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  • by Shaunixie on April 17th, 2009

    Shaunixie

    I would ask the man who always lies which door it is.

    He states he always lies, but that in its very statement is the truth.

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  • by lillies98 on March 21st, 2010

    lillies98

    i'd ask something like "what color is my shirt?" depending on his answer i'd know which one is lying

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  • by SarahEatWorld on August 23rd, 2008

    SarahEatWorld

    Where did i put that cupcake?

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  • by bloodlylilcorpse is back on April 17th, 2009

    bloodlylilcorpse is back

    I'd look both square in the eye, and say, "Which ones the the door?"

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More Questions. Additional questions in this category.

You're reading Riddle:A man is sentenced to death but he gets to choose the life door or the death door. there are only two doors and they look exactly the same. there are two guards, one tells the truth always and one always lies.you can ask 1 question what is it? - which can also be phrased in the following ways:

  • You are in a mine with 2 exits, one leads to death and one to escape but you know not which. Also each exit is guarded by a being one who always lies and one who always tells truth but you know not which.With only one question how do you escape?
  • You have been put into a room with two doors. One leads to death, one to freedom, with a guard at each door. One lies, one is truthful, you don't know which is which. After one question you must go through a door...what's you question?
  • There are two robots, one tells lies, the other the truth. They are guarding two doors, one to life, one to death. You don't know which robot is guarding which door. You can ask one robot one question to find the door to life. What do you ask?
  • Two doors are guarded by angels,you got to choose the right one that leads to heaven but you may only ask each guard the same question once. by door no 1 the guard can only tell lies and door no 2 the guard can only tell the truth,what is the question?

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