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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 ...
Go to the full post

94 replies to this topic

### #81 peanut

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Posted 24 September 2010 - 05:33 PM

i tried alot of direct question like that but its never right all the way, its solve 80% of the possibilities but not 100%

like now in the third possibilities you put (if m1 is T or R, m2 is L or R then m3 canot be R and has to be T or L)

but m3 can be the R, if m1 T and m2 L then m3 will be R

so in this case m3 can be R,T,L and we have one more question to go which make it impossible

Snap, I missed that somehow.
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### #82 Zak

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Posted 25 September 2010 - 12:50 PM

peanut i would like to know what you think about my solution, do you agree with me or not
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### #83 swongy

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Posted 18 October 2010 - 04:37 PM

Get the 3 person to stand in one straight line.
the 6 possible lineups are TLR TRL RLT RTL LTR LRT, where T = truthful guy, L = liar, R = random guy whose capable to lieing and telling the truth.

Qns are asked to determine the possible lineups in that group

Qns 1 ( to the 1st guy in the line) " is the L standing directly on the right side of R"

Yes : TLR RLT RTL LTR
No : TRL RLT RTL LRT
Qns 2 ( to the 2nd guy of the group who answered Yes) " is T in the group" *to the group who answered no, ask the qns to the 3rd guy instead. This should eliminate the possible groups down to two

Yes : RTL LTR
No : TLR RLT

Qns 3 ( to the 2nd guy of the group who answered Yes) "is the lineup as follow RTL)

Yes : RTL
No : LTR

Edited by swongy, 18 October 2010 - 04:42 PM.

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### #84 ndm20

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Posted 29 October 2010 - 09:49 AM

Spoiler for Here's one simple answer:

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### #85 Joaquin Galvez

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Posted 15 November 2010 - 08:53 PM

Spoiler for Here's one simple answer:

This method works, but it's technically 4 questions (the London question asked three times, one for each guy) and the fourth to either the T or L to find the solution.
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### #86 Brainiac_1996

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Posted 21 December 2010 - 04:17 AM

Spoiler for Simply put spoiler

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### #87 chang

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Posted 29 December 2010 - 11:30 PM

Picture the three persons next to eachother in a row. By asking the first and last guy in line who the guy in the middle is, and by asking the guy in the middle who he is - you can use the statments to figure out who is who.

Test and see for your self!
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### #88 bartf

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Posted 31 December 2010 - 05:52 PM

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### #89 Brandongoh

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Posted 25 September 2011 - 03:19 PM

How can i see the answer of WritersBlock?
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### #90 Kia

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Posted 27 September 2011 - 03:04 PM

The trick to this puzzle is to force the liar into a double negative situation, and also to remember that the Random guy does not give random answers, but that he randomly tells the truth or lies. The key point is that he sometimes behaves like the truth teller and sometimes like the liar.

So you go to the first one and ask him "if I were to ask you 'is the second person is the random guy', would you say yes?"
If the first person is the truth teller, then it is easy, he would say yes if the second person is the Random guy and no if not

If the second person is the liar and the second is the truth teller, then the liar would have said yes to 'is the second person is the random guy' but since he is still telling lies, he would say no.
If the second person is the liar and the second is the Random guy, then the liar would have said no to 'is the second person is the random guy' but since he is still telling lies, he would say yes.

So in both cases, the truth teller and the liar would clearly indicate if the second guy was the Random guy.
Now what if the Random guy was the first person?
He would say no if he was acting like a truth teller
and he would say no if he was acting like the liar

So after the first question you know if the second guy is the Random guy or not.

If he is not, then you ask the second one a similar question
"if I were to ask you 'is the third person is the random guy', would you say yes?"

For the same reasons as above, after this question you know for sure who the random guy is.

Now there is one more thing left, to find which one tell the truth and which one lies, and again, a similar question from the third person
"if I were to ask you 'is the first person is the truth teller', would you say yes?"
or
"if I were to ask you 'are you the truth teller', would you say yes?"

and you know which one is which. The whole key is to ask a question

As I said, the trick to this puzzle is to force the liar into a double negative situation, and remember that the random guy either tells the truth or lies which would mean that the follows the same thinking patters as the liar.

I hope that was clear
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