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The liar, the truth teller....and the random answerer


Best Answer Writersblock , 30 July 2007 - 01:31 AM

Martini,

Spoiler for ...
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94 replies to this topic

#31 Gaunt

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Posted 07 May 2008 - 02:25 AM

There are actually two men who can't answer, not one, so the solution the way you proposed it won't work. Also, it assumes that not answering is permissable, so the random answerer can also choose not to.


"if B says yes, then you ask the L (the only one that lied) who the T is"

What if two of them lied?



I don't see how two men can't answer, as only one was asked an unanswerable question. And since the random answerer must either lie or tell the truth, i disagree that he could choose not to answer.
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#32 Martini

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Posted 07 May 2008 - 02:45 AM

I don't see how two men can't answer, as only one was asked an unanswerable question. And since the random answerer must either lie or tell the truth, i disagree that he could choose not to answer.

Okay, I got you now. That's actually pretty clever. The only problem I have with it is assumes that not answering is an option. If not answering is an option for the one that can't answer without knowing if his statement will be truthful or not, why can't any of them decide not to answer? Besides that, I like the logic.
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#33 Little-Jim

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Posted 18 May 2008 - 12:20 PM

There is a truth teller (always tells the truth), a liar (always lies), and one that sometimes answers truthfully and sometimes lies. Each man knows who is who. You may ask three yes or no question to determine who is who. Each time you ask a question, it must only be directed to one of the men (of your choice). You may ask the same question more than once, but of course it will count towards your total. What are your questions and to whom will you ask them?



Using slightly oblique questions and given that the two consistent answerers are obliged to follow their path (ie the truth teller has to be right and the liar has to be wrong) . Would it not be possible to follow a line by which an 'I cannot answer that' answer is forced - providing the necessary piece of info.

i.e To any given person - "If I asked him (one of the other men) the question 'is the sky blue?' what would his answer be?"

As soon as a 'I cannot answer that' repsonse is gained, you know the subject of the question is the random answerer.

The only man who could answer that question about both the other men is the random answerer. Leaving a full question to deduce the other's identities with a simple question you know the answer to. Ie Is the sky blue?
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#34 Ignored Genius

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Posted 27 May 2008 - 12:58 PM

Hi,
I don't know if this counts but I hope it does.
These are the 6 possible ways they may be standing.
1 2 3
T L R
T R L
L T R
L R T
R T L
R L T

If you ask the 1st person, "If I were to ask the 2nd person if the 3rd person always told the truth would he say yes?," three things will happen. You will get either a yes, no, or no response. The only one who will be able to give a yes/no answer is Random. The truth teller and the liar will be stuck without an exact reply. So, if the was no response then you have narrowed the order down to:

1 2 3
T L R
T R L
L T R
L R T

Now, you ask a similar question to the 2nd person. "If I were to ask the third person if the 1st person always told the truth will he say yes? You will once again have three things happen. You will get either a yes, no, or no response. If you got a yes/no then they are the Random. No response implies truth teller or liar. So, if you received no response then this will be the remaining choices.

1 2 3
T L R
L T R

Finally, you ask the 1st person if the 3rd person always tells the truth. Seeing as you know the answer to that you will automatically know if they are telling the truth or they are the liar. That is the easiest question I could think of.

Theoretically you could solve this in 2 questions if the first person gives you a yes/no answer on the first question because you will know they are the Random on the first shot. Like I said, I don't know if this solution counts but I wish this was a real scenario so I could see these guy's reactions when I asked them the questions. LOL
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#35 elemancer

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Posted 06 June 2008 - 03:09 PM

To be honest a "No response" type of solution is a little cheating...but I do have a way to solve this:

1. Ask the first man of the second man: Does he lie or tell the truth?
2. Ask the second man of the first man: Does he lie and tell the truth?
3. Ask the third man of the second man: Does he lie or tell the truth?

Here is the decision tree:
Note, the man on the left hand side of the arrow is the askee and the man on the right hand side is the subject

Question 1 - Ask the first man of the second man: Does he lie or tell the truth?
We can determine if

A yes will yield:
T->R
T->L
R->L
R->T

Basically, the first man is either the Truther or the Random guy

A no will yield:
L->R
L->T
R->T
R->L

Basically, the first man is either the Liar or the Random guy


**
Question 2 - Ask the second man of the first man: Does he lie and tell the truth?


If a yes was given for question 1, question 2 will yield:

A yes will yield:
R->T
L->T

NOTE: This will tell us the first one is the Truther, and the third question should simply be asking the truther if 2 is the liar.

A no will yield:
R->T
L->R

Move on to question 3...

If a no was given for question 1, question 2 will yield:

A no will yield:
R->L
T->L

NOTE: This will tell us the first one is the Liar, and the third question should simply be asking the liar if 2 is the truther.

A yes will yield:
R->L
T->R

Move on to question 3...


**

NOTE at this point, the results of these answers cancel several possibilities, leaving us with only two possible positions depending on the branch we're on (Yes, No or No, Yes)


Question 3 - Ask the third man of the second man: Does he lie or tell the truth?

If the previoues two questions were Yes, No

A yes willl yield
T->L

A no will yield
L->R

Either answer tells you who the last two are...

If the previous answers were No, Yes

A yes will yield
T->R

A no will yield
L->T

Either answer tells you who the last two are...



/end

It's a little convoluded, but the basic idea is to force the response of the liar/truther to find the random guy. My BIG assumption here is that Yes/No logic follows standardized logic (True/False) where the liar simply states the inverse answer to the question. For instance, if I'm asking the liar if the random guy lies and tells the truth, the liar MUST answer no whereas the truther MUST answer yes.
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#36 jadedkidd

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Posted 10 June 2008 - 02:27 PM

i think i have it.... ask two of the men if they are men ? truthful answer is yes the liar could only say no since that would be the lie(obviously)......... therefore ,singling out the liar, then you ask the liar to tell you out of the other two which one always tells the truth(must specify him to tell you based on the other two otherwise he could say himself).... since he lies he will tell you the one who is the random answerer.....................
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#37 Slick Nick

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Posted 11 June 2008 - 12:35 AM

Keep asking the men if they are the liar and when one of them says yes he is the random man...lets lable them L T R

We have eliminated R it might take a few times but that is the only possible way to elminate him is to keep asking.

Now ask either the L or the T (the two left) but since we dont know which is which we will say 1 and 2

Ask 1 if 2 would say he is a liar if 1 says YES then he is the one telling the truth if he says NO then he is the liar.

THIS IS THE SOLUTION im sure there are probably more ways but this is the easiest ;)
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#38 Asdfgh Zxcvbn

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Posted 15 June 2008 - 02:03 AM

There are actually two men who can't answer, not one, so the solution the way you proposed it won't work. Also, it assumes that not answering is permissable, so the random answerer can also choose not to.


"if B says yes, then you ask the L (the only one that lied) who the T is"

What if two of them lied?


Well Martini, i already explained that if 2 of them lied, then you should ask the T (the one that only told the truth (you know, the second part of my first answer (and yes, i did use 3 brackets at once))) who is the liar and the both

<_< -_- :huh: :mellow:
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#39 Martini

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Posted 15 June 2008 - 03:37 AM

Well Martini, i already explained that if 2 of them lied, then you should ask the T (the one that only told the truth (you know, the second part of my first answer (and yes, i did use 3 brackets at once))) who is the liar and the both

<_< -_- :huh: :mellow:

You don't get four questions; you get three.
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#40 smarties

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Posted 15 June 2008 - 10:01 AM

so we have three people in a room, number 1, number 2 and number 3. One of them speaks only the truth(T), one can only tell lies(L) and one can do both(B).

my first question will be directed to all three of them:''Is there anyone among you three that only tells lies?''

I know that T will say yes to this question and that L will say no. So depending on what B will say I have two possibilities:




1) the answers i get are: yes, no, yes(if B will tell the truth)

lets say that i get the answers in that turn: 1=yes, 2=no, 3=yes. Then i will know that 2 is L. I will ask him if 1 is the truthteller.

If he says yes then i will know that 1=B, 2=L, 3=T. If he says no then I will know that 1=T, 2=L,3=B




2)the answers i get are:yes, no, no(if B will lie)

Assume that i get the answers in that way:1=yes, 2=no, 3=no. Then i will know that 1 is T. I will ask him if 2 tells only lies.

If he says yes then i will know that 1=T, 2=L, 3=B. If he says no then i will know that 1=T, 2=B, 3=L
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