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  • You could just ask a really obvious question. Like "Is the sky blue?" (assuming the sky is blue at that moment). Then it's easy to see who's the liar and the truthteller.

  • Can you ask one of them a question you already know the answer to know who lies and who tells the truth?

  • Comment removed

  • I would've:

    A. looked at their eyes because you can tell someone is lying by their eyes. The police use that technique all of the time

    or...

    B. I would've asked the two to go and open their door, if they are hesitant it's obviously the other, and the other one will open the door and I will find the treasure. Therefore, I win either way.

  • @UberGamer1030 cool story bro. u need to understand the situation first, u only had one question and can only ask one of them. If everyone can notice if someone is 100% lying by just looking at the eye, then nobody would lie. Lol. nice try though smart-wanabe.

  • @FrYLocK41 Sure, that goes for some, but I myself am doing this, and not anyone else. We're not talking about anyone else but yourself.

  • I don't understand how this gets you the correct advice.. Anyone mind explaining it to me please? :s

  • @TheRealMrBillyBob You only have one question. One guy lies, one guy tells the truth. If you ask the honest guy "what would the other guy say is the correct door?" The honest guy would obviously tell the truth and say that the other guy will tell you to open door 1 (incorrect door) because the other guy is the liar.

    Now if you ask the liar the same question, he would lie about what the honest would say and will tell you to open door 1 as well. So obviously door 2 is correct.

  • I would ask what is the color of the door that they're sitting besides. Problem solved.

  • my ways a little different. I would ask do i have brown hair(i do) if it he says yes i know hes the truthteller. i then would ask the liar which door leads to riches and pick the opposite. would this way work too?

  • @twistedshadows87 No since you only get to ask 1 question, same problem with alot of the comments, finding out who tells the truth or not wont work since you would not be allowed to ask which door it is

  • i would ask " 1+1 = ?"

  • @MrZajoxxx yes but then you would be stuck without a question and have no idea which door to open. the other way to get the right door is instead of asking what door would the other guy say is correct, you could ask what door would the other guy say is incorrect, then go by what they say

  • @MrZajoxxx You only have one question. If you ask 1+1, you will know how the liar and the truthteller but you wouldn't be able to ask which is the correct door anymore because you already used your one and only question.

  • this is a great puzzle but so much of the video's time could have been shaved off if you just did a little editing.

  • I like to think of it as Boolean multiplication.

    0*1=1*0=0

  • i should not be so stoned when i watch this vids...

    So who knows when the train comes ¿

  • Haha I get it now but I was stumped b4 haha that was good!

  • ask the door

  • fuck watching this while high is intense.

  • It's interesting, because you don't actually NEED to ask about the other guy.

    In asking either the liar or truthteller what the other guy you said, you are essentially asking him what his opposing personality would say. Thus, if you ask him what he would say, given his honesty is the reverse of what it is, would get you the correct answer.

    A question along the lines of "If your truthtelling habits, were the opposite of what they are, which door would you tell me to open?" will do the trick.

  • Oh. ;_; I thought only yes/no questions were allowed.

  • This was new to me and took me approx. 30 secs to figure out the bulletproof method. So for me, it was very easy.

  • I think there was something like this in a Yu Gi Oh episode lol

  • @plamenxyzpenchev Thats's correct I think, the problem is I was 6 years old when I saw it and didn't understand a thing of what was going on :D

  • This brain teaser was featured in the Labyrinth

  • How do you know if the person you ask the question to is telling the truth or lieing?

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  • @marcusmondragon21: The liar MUST always lie. So he will definitely lie about the truth teller's answer. That is why we are sure that the final answer is always incorrect (agony door)

  • This is flawed. What's to say the liar wouldn't lie to me about what the truth teller would give me? He could lie to me just to get me to open the door of misery!

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  • This reminds me of the season final of the Mentalist from season 3.

  • I would stab one of them in the leg. Whichever one cries "it hurts," would be the one I ask which door is correct.

  • @Catastrogue FUcking genius.

  • @Catastrogue That's not the solution, because you get to ask question and that is not the question, but the action and that would not give you correct answer.

  • Nice! Now I know what to do next time this happens to me. :}

  • The problem its not about getting who is telling the truth or lying but about getting the same answer of the question by both, it also works with asking what its the incorrect door and opening that door.

  • At this point i think that the brothers will have caught on to the fact that everyone has figured them out and decided that they both will lie

  • Ahh ha just got it, its better to put yourself in the situation

  • I guessed right

  • I'd walk away.

  • why don't you ask the guy what 1+1 is? :P straight forward

  • @jobinjohn1992 Because you can only ask one question and figuring out which one is the liar doesn't help you pick which door to open because you can't ask a follow up question.

  • @jobinjohn1992 you still can't ask a second question.

  • Interesting .. I had to rewind for sec when u talked abt d 2nd incorrect door, but it makes sense .. Good job sal!

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  • The day when the liar says he is the liar.

  • I also think that since they know the correct door, if you ask them a question like "Do you know which door is correct?" liar would say "no".

  • @JimmyNovik

    But you only have one question! That would only tell you who the liar is. You'd still have no clue which door to take.

  • @JimmyNovik No you dumb ass, the liar would give you the wrong door but you wouldn't know it's the wrong door because one of them tells the truth and you don't know who's who.

  • @JimmyNovik But you can only ask ONE of them the question.

  • You know that both of them know from eachother if t hey're either always lieing or telling the truth. So you could also ask one of them: Do you know if this other guy is always telling the truth? If he says he doesn't know it he is lieing because they know from eachother if they're always lieing or not 1:40. If he says he knows it then he is speaking the truth because the other guy who is always lieing would say he didn't know. :P

  • "The God of brain teasers told me..." LOL!!! Sal, love your videos although they could be 2 min long. You just talk and talk and talk... :)

  • basically they will both give incorrect answer, bad explanation lol

  • Ok....Sal, I just love your brain teasers...but all of these videos could be so much shorter... I'm sorry, but you talk SOOOOO much...I can't believe it!

  • I'm sorry but i still dont get how you would possibly know which guy is the liar or the truth teller 0_@

  • how did u put that download button? please tell..

  • easy duhh... which one is the door? lol

  • I don't get it. I think..

    but are u saying that basically if you don't knoe wat to do, u do the oppisite of what they tell you to do?

  • I love your videos, but dis your explanation sometimes is confusing, I think it's better to write it down.

  • Got this in 12 seconds! Haha, lucky guess.

  • What if the liar lies to tell the truth?

  • @jataka3 the liar wouldn't tell the truth because it's not within his nature to tell the truth. he has to tell a lie. it's like the twiins who arn't. "they're both the same person but one is a fake and wants to stay with you" the fake one will like and the real one will tell the truth.

  • @Freeruningmonkeys lol!!! Maybe that is the best solution...because in that situation I would probably give up in a few minutes and go home without treasure, but alive! :)

  • If he says that the BROWN guy would suggest door 1, then you go to door number 2.

    That's totally not racist XD

  • It's easy, grab both by the shoulders and shove them towards a random door.

    If they resist, it's the wrong one.

    No questions asked.

  • @nuclearpsychopath Chuck Norris, is that you?? ;)

  • why are ppl so confused the explanation is fine..

  • i would ask one of them which one is the door to happiness is and then have them walk in first, that way if its horrible death then i'm not the one dying

  • What I you asked "Which door would the other guysay if the incorrect door?" Would that make both guys point to the correct door?

  • @SensiStarToaster, NICE! That's correct, they would both be pointing the correct door, by saying that the other guy will tell you it's the incorrect door. Very nice brainteaser, cause you never know who the actual liar and truthteller is. Is it true that we depend on the liar more to solve the brainteaser?

  • Man, I've got to say: I love your calculus vids.They help me a lot.

    But you usually lose yourself in your explanations: right now It took you nearly 7 minutes to say SOMETHING SO SIMPLE in this video.

    I was so bored I went straight to the end.

  • This also works for the same question but with "wrong door" as I so correctly predicted before I resumed the video because IM SO FUCKING SMART IM THE NEXT STEPHEN FUCKING HAWKING! IM IN HAWKING POSE RIGHT NOW IN MY CHAIR AS I TYPE THIS.

  • This is on Khan Academy and I watched it already and got 750 energy points.

    I have: 172696 energy points. I have 72 total badges.

  • that doesn't make sense. if you pick the opposite door than your chances of survival is 50/50. plus even if you ask either one of them the question, there is no way you can tell if they are lying or being honest. I don't know, i find this brain teaser to be stupid, mainly because you are setting your self up to die if you ask the the wrong guy the question and ending up opening the wrong door.

  • @gameshop101 no... both possiblities are given, you can either ask this question the the guy who always lies or the guy who always tells the truth, the guy who lies will answer the opposite of the correct door ( because the person telling the truth would answer the correct door), the guy who tells the truth knows that the other guy lies and will tell you that the guy who lies would say this door which is the wrong door because he lies... hence either way the answer is the incorrect door.

  • it still is a 50/50 chance.

    1 is good, 1 is bad,.

  • You should redo this because the explanation really sucks. Do you really only get 1 question? Is it 1 question per guy? Because the way you explain it only works if you have multiple questions... *confused*

  • I would ask him if it was true that I'm standing in front of him, if he was the truth sayer then he would say yea, if he was the liar he would of said no. thats what I thought was the correct anwser it still makes sense to me.

  • @TheMountainlotus But thats the only question you get to ask (only 1 Q.) you still need to find out what door to open... you can't ask anymore questions...

  • @TheMountainlotus yeah but you still wouldn't know what door is the right one ...right? Just because you know the liar, doesn't mean he is in front of the door to hell or w/e

  • if you ask one of them "which door will the other guy tell me to go through if i asked him which door is the treasure door?"

    then you'll know which door is the door of despair

    if you asked the liar he would lie and tell you to go through the bad door

    if you asked the person who is tells the truth he would also tell you which one is the door of despair......i think :D

  • @Freeruningmonkeys lol you explained it much better....

  • @Freeruningmonkeys brilliant!

  • What if the liar says "I don't know"?

  • @Pscool17 then punch him in the head

  • @Pscool17 LOL

  • @Pscool17 he was to lye or tell the truth and he knows so he can't say that

  • @nowenterme1 By saying he does not know, he is obviously lying, as he knows.

  • @Pscool17 sorry meant has not was

  • that was worth 2 min not 7!

  • I love this : DDDD

    I remember this appearing in a Powerpuff Girls episode.. and somewhere else

  • there nothin so intelligent why make thevidio 10 mins if its poss 2 mak it in 2min i was dissapointed aftr i saw this frm khnaca aftr so much praise frm my frnds lets see if they hav nythin bttr

  • why not ask them "what is the best question to find the right door" and if the answer makes sense then hes the truth teller, it not the liar.

  • I had heard this before. I think you're supposed to mention that the guys "know everything" or that both guys know who is the truthteller and who is the liar. As it was explained here, you wouldn't expect the guys to know what the other one would answer. No?

  • Ok. I'm at 2:03 and I think I've figured it out. You ask them what color or shape is something and the person who lies would tell you the wrong shape or color, so you would ask the truthful person which one's the door. Yippe?

  • @TGDproductions that would work, but you have only one question to ask just one of them.

  • @splattiful Ye I didn't read it was one question sorry ><

  • @TGDproductions Well you can only ask ONE question =)

  • @TGDproductions But you can only ask one question

  • I would ask: "is the door in front of the lier the correct door?" I think you would get the same answer.

  • I can't believe you've drawn such dastardly looking fellows.

    WHAT FIENDS!

    I have nightmares involving their smiley round faces.

  • How about you hold up, say 4 fingers, and ask one of the guys "How many fingers am I holding up?". The liar would lie, so you would know that his door is the bad door, and the truth teller would tell the truth, so you know his door was the correct door.

    Of course making sure not to use any thumbs so he can't get you with the whole "thumbs aren't a finger!" thing.

  • @RS1Comedy1Vids in this case you would only know the liar and the truth teller but you wont know the right answer to which one is the right door... and you have to ask only one question

  • @monikaable63

    Oh right, I thought the liar was guarding the bad door and the truth teller was guarding the good door. My bad.

  • @RS1Comedy1Vids

    That would not work because a.)the liar could be sitting in front of the correct or incorrect door. and b.)that only eliminates one of the two problems and determining who is the liar and who is the truth teller is only that...it would not tell you which door is correct because you can't ask them a second question which obviously would be "which door is the correct door?" after you determine that they are the liar or truthteller.

  • oh my god this is awsome

  • I got an alternate question that achieves the same result:

    "If you were the liar and I asked you if the treasure is on the right, would you answer yes?"

    This will get you the door to NOT go through, because the liar will lie about what he would otherwise say.

  • @RickW05 no in this case the liar will lie and tell you the correct answer and the truth teller will tell you the wrong answer.. so its still the same thing..

  • @monikaable63 Dang! You're right!

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  • @grouchysin we all know what definition the riddle referred to.

  • @hanashinki UH yeah he did. Did you like actually watch the video? References to treasure and or infinite happiness: 0:46 , 1:19 , 5:28

  • what if instead you ask one of them which door is the right door. the liar will say the left door and the truthteller will tell you the right door. if depending on if they explode or not for making them say something both true and false you will know which door it is.

  • Of course, this depends on your definition of a lie. A lie is sometimes defined as a false statement, but it is also sometimes defined as a statement that intends to mislead. If you asked the liar "What door would the other guy say to open", the liar would work out why you were asking this question and actually misleadingly tell the truth in this instance, thus misleading you into opening the wrong door.

  • @kristijanadrian if the guy in front of the door was the one who guarded that door and there were two doors, with a guy at each one, and one told the truth while the other lied, the one who lied guarded hell and the other one guarded heaven, kind of like in the video, there would be a different question like "is my shoe untied?" and so you would ask either one, you'd know what they were thinking by checking your shoe and if they told the truth, you'd go through that door. why go to hell?

  • @kristijanadrian no it works! if you ask the truth telling guy or the liar you get the incorrect door for ex. with honest guy he'd say "the other guy would say to go to door 1" if you ask the liar he'd say "the other guy would tell you to go to door 1" and they know if they lie or not. in other words they know who they are. the truth telling guy would say "the liar would say to go to door 1" but he wouldnt say "the liar" it works if you know who they are or not. to be continued...

  • or if the guy in front of the door was gaurding that door and same with the other guy, you ask if your shoe is untied or unvelcrowed

  • Labyrinth  lolz

  • knock knock knock... "BE HONEST WITH ME OR YOU'RE DEAD, IS IT RIGHT DOOR I SHOULD OPT FOR!?"

  • door, door, door.. who asks these stupid questions...

  • okay, so my answer was... ask the green guy if he was green, if he said no, then you ask the brown guy which is the door with the riches... i thought that was a lot easier to explain... then all that

  • @ThenameisDre

    You only get to ask one question to one of the coloured guys. The question you get to ask in the video...means it doesn't matter which guy you ask...you simply do the opposite.

  • what about reverse psychology?

    i mean they both know ur gonna go to the opposite door than the one they tell u is good.so they will tell u the correct door and u will end up going to hell(wrong door).

  • i thought of a question about it. just tell me guys if you agree with it.

    so, my question, "is this a door?"

    and if it happened that the guy was the liar, well according to what i heard the liar could not help himself but to tell a lie, of course he will say "NO". and according to what he answered i already know that he's the liar and i already know that the other guy is the truthteller and i will now ask him w/c is the correct door. ssee?

    and if it happened that i asked the honest first, easy.

  • what if there's 3 guys? One always tells the truth, one always tells a lie, the third guy stabs people who ask awkward questions.

  • 11 people picked the wrong door.

  • ask the green guy whats five times and if hes right then go into the door thats near him if hes wrong go in the other room

  • @skylerroxtheworld2

    Except nothing guarantees that the liar is in front of the wrong door - he may well be in front of the correct door, in which case you'd lose. I had considered the same question initially, the problem is that you only have one question and with that question you must do two things;

    A) Figure out who's lying

    B) Figure out which door is right.

    Your question only does the first. The videos question accomplishes both.

  • come on i stood there thinking for a few minutes and there is no way to get the correct door?

  • You can also ask them (one of them) "What door would you tell me to open"

    (ofcorse without the spelling and grammer mistakes...)

    Both will choose the correct door.

  • @ILIYYILI

    No... if you did that the truth teller would tell you the right door, the liar will tell you wrong door. In which case you haven't learnt anything.

  • @Vire70

    No.

    The truth teller will point at the correct door.

    The lier will point at the correct door too, because if you asked him what's the right door, he would tell you the wrong door, and now you're asking him what would he say and he has to lie.

  • @ILIYYILI

    No... only one question of each door keeper is permitted. If you ask the liar what door he will tell you to pick - he will tell you the wrong door. If you ask the truth teller what door he will tell you to pick - he will tell you the right door. Both doors will be different, and you'd have no way to distinguish between which was true or false.

    Bare in mind that you don't know which is the truth teller or liar.

  • @Vire70

    I know.

    But I ask him only one question:

    "If I had asked you what is the good door, what would you tell?"

    If the person happened to be the truth teller, he will say the right door.

    If he's a liar, he will have to do a 'double' lie, therefor tell the truth.

  • watch this video 'Maths Brainteaser' by fm2011fan

    see if you can solve it

  • Now there's 3 people: One always tells the truth, one always lies, and one is packing heat and shoots anybody that talks to him

  • @rotflmaopmpqxyz thats so fucking funny

  • i'd rather trust a martian than a brown man...

  • another solution: you as, what would you say yesterday.

  • Will it blend? That is the question.

  • this is an interesting brain teaser but an absolutely horrendous explanation.

  • @darkcity925 Tell that to Bill Gates! :-)

  • Ask one of them "what would the other guy say"?. The liar would say door number one because he lies. The truthteller would say door number 1 because he knows that he always lies...so u choose the opposite

  • I got another solution. NEVER trust the brown guy! hahaha :D LMAO

    jk im brown :) you can trust me haha

  • I would ask how many doors are there... much simpler :)

  • @jovanm91 actually thats not gonna work because finally you cant find the correct door,,,,, u just find the liar!!

  • @sshhaahhaabb yeah i forgot, you can only ask ONE question XD I FAIL

  • @jovanm91 wrong!! by asking that question you will not find the correct dor ;)

  • @drgshnbs I already corrected myself read the comments

  • the question and answer is correct! you'll see similar story in the bible., I mean this really comes from a bible but they change a version a bit.

  • this is just like one of the episodes of samurai jack.

  • ask the liar and take the other door

  • wat a complicated explanation..u made it so complicated wen it realli isnt...but i knew dat one already

  • hey they may say door no 2 or 1 it is not neccesary he tells incorrect door

  • nice warm up brain teaser not bad.

  • just tell one of them to open a door if there is money you win if he dies you open the other door...

  • what a complete bullshit and a waste of time

  • A more fun question would be: "Now open the fucking correct door, or do you want me to kick the shit out of you?"

  • please post more brainteasers!!!!!!!!!!!!!!!!!!­! i loved all of them!!!!!!!!!!!!!!!!! i especially liked the ones like this one and the forhead problems! :D thanks!

  • T+F=F , F+T=F , !F = T

  • @itsaji never knew logic class would help so much

  • Well considering the colors of the two faces green and red I would ask the Green lightm are you really demonstrating your color. Green for go Red for stop, I would use the color for defining the correct door.

  • Cool I figured it out really fast!

  • My question is, if two guys are sitting outside of a door to infinite wealth and riches and they both know which one it is, why hasnt either of them opened it yet?

  • @roxy2190 excellent observance Rox

  • Why would you ask a question to someone who always lies? That's my question.

  • @Emanresu56 You dont know which one lies..

  • or u can just ask one guy is hes a girl and i he says yes then hes the liar and the other dude is not, then u can just ask the other dude which door is safe and he will answer correctly :)

  • @123lilpimp123 pause it at 2:28. The red writing will stun you

  • @Mcplumpyboy lol yea i just realized that lol my b -_- feel so stupid now lol