Truth or Lie?

A forum for good logic/math puzzles.

Moderators: jestingrabbit, Moderators General, Prelates

User avatar
Posts: 60
Joined: Fri Oct 02, 2009 4:18 pm UTC
Location: Paris

Truth or Lie?

Postby Ddanndt » Sun May 30, 2010 7:55 pm UTC

Hi everybody. Just wanted to share a small puzzle with you.

" I'm making my way in the Amazonian jungle and I come across three persons who either come from Clan A ( always speak the truth) or the Clan B ( always lie) . I ask them from which clan the come from : the first answers me but for some reason I dont hear him, the second repeats what the first says( i assume) and the third tells me from which clan the first and second come from. How to I deduce the answer? "
Last edited by Ddanndt on Tue Jun 01, 2010 1:20 pm UTC, edited 1 time in total.
God does not care about our mathematical difficulties — He integrates empirically.
—Albert Einstein

Posts: 46
Joined: Tue Oct 14, 2008 11:15 pm UTC

Re: Truth or Lie?

Postby bane2571 » Mon May 31, 2010 3:47 am UTC

The question is a bit ambigous. Are they all from the same clan? Did you deliberately leave the content of 3's answer out?

Posts: 2
Joined: Tue May 04, 2010 2:57 am UTC

Re: Truth or Lie?

Postby presson312 » Mon May 31, 2010 3:50 am UTC

All that I've been able to deduce so far:
Persons 1 and 2 must have both claimed to be from Clan A. (Seems obvious, but I'll explain anyway, if you already know, skip it.) People from Clan A will never claim to be from Clan B. People from Clan B will never plan to be from Clan A. For similar reasons, Person 3 must claim that he himself comes from Clan A.

Person 3 can either verify or negate Person 1's response. If Person 3 verifies Person 1's response, then Persons 1 and 3 must come from the same clan. If Person 3 negates Person 1's response, they must come from opposite clans.

I have no clue as to how to begin guessing at Person 2, unless you meant that Person 3 says where Persons 1 and 2 come from.

User avatar
Posts: 60
Joined: Fri Oct 02, 2009 4:18 pm UTC
Location: Paris

Re: Truth or Lie?

Postby Ddanndt » Mon May 31, 2010 6:28 am UTC

Person 1 will always claim to be from clan A , so if Person 2 answers A he's telling the truth and is from A or else Person 2 is from B. And from there you can verify where Person 3 comes from and then Person 1...
P.S Person 2 can repeat the opposite of what he heard if he's a liar :twisted:
God does not care about our mathematical difficulties — He integrates empirically.
—Albert Einstein

User avatar
Posts: 643
Joined: Fri Feb 08, 2008 6:01 am UTC

Re: Truth or Lie?

Postby thc » Tue Jun 01, 2010 5:46 pm UTC

Please fix the grammar and ambiguity, because the question is not clear. I don't think you've thought this through all the way. There are two different sets of cases that produce exactly the same answers:

From the person 2's answer, we know that both 1 and 2 are from the same clan, but not which clan. If 1 and 2 are both from clan A and 3 is from B, then 3 can say that 1 and 2 are from B (lie).
If 1 and 2 are from B and 3 is from A, 3 will say 1 and 2 are from B (truth).

Similar results for when all three are from A vs. all three from B (person 3 will say that they are from A). So in actuality, you can't determine which clan each person is from.

Posts: 116
Joined: Tue Dec 15, 2009 9:17 pm UTC

Re: Truth or Lie?

Postby redrogue » Tue Jun 01, 2010 7:46 pm UTC

Is 'no' your answer to this question?

Posts: 387
Joined: Fri Apr 02, 2010 1:51 pm UTC

Re: Truth or Lie?

Postby Trebla » Tue Jun 01, 2010 8:42 pm UTC

It seems there are many different ways to interpret

From "I ask them from which clan the come from" I would assume that he asks them, in order, "What clan are you from?" and that is the only question asked.

Since, regardless of truth vs. lie of each individual, they will always answer "Clan A".

The rest is a bit of a mess and implies you have an external knowledge source.

The first answers "Clan A" (but you don't hear him, but it's the only possible answer).
The second answers "Clan A" which is a repeat of what the first said because it, also, is the only possible answer.
The third answers "Clan A" which, again, is the only possible answer, but you have the additional information that the third person's answer is the Clan that the other two both came from. So you know they both came from Clan A, but there's no way to determine which Clan the third person is from.

Yeah, clarity in the riddle is needed.

Posts: 240
Joined: Wed Nov 21, 2007 1:16 am UTC

Re: Truth or Lie?

Postby fyjham » Wed Jun 02, 2010 3:06 am UTC

So person a and b claim to be from Clan A, because they would regardless of their clans. Person c, who could also be from either clan, tells us what clan the others were from (Either honestly or lyingly based on his clan). It's a bit vague as to whether a, b and c are all from the same clan or potentially different clans, but either way I don't think we can work anything out based on the following:

assuming a from A, b from A, c from A
a says a from A (truth)
b says b from A (truth)
c says a from A, b from A (truth)

assuming a from B, b from B, c from B
a says a from A (lie)
b says b from A (lie)
c says a from A, b from A (lie)

Therefore simply by showing 1 case where the same information is provided when the tribes are completely different we show we can't determine what tribes they're in from this information. From which I determine it's either impossible to determine or there's some external information we're meant to be spotting other than the people's answers (Which would probably be a bit 169, but I hold judgement till knowing answer).

You can split the results into 2 clans, the ones c agrees with are in c's clan, the ones he disagrees with aren't, but I can't see any facts that could be used to label those two groups as Clans A and B respectively.

Edit: I think I misinterpreted the statements cause I thought of an interpretation where it can be solved
Assuming we take the statement as the questions:
To Person 1: What can are you from? <Don't hear answer>
To Person 2: What did Person 1 say? <Hear answer>
To Person 3: What clans are person 1 and person 2 from? <Hear answer>
We can say the following:
Person 1 will always say he's from clan A (Either from clan A and says truth or B and lies), so if person 2 says that person 2 from clan A, otherwise person 2 is from clan B. Based on this when Person 3 tells us what clan person 2 is from we can deduce if he's lying and hence his clan, then based on whether he lies we know what clan person 1 is from (Either it's what he said or the opposite based on if he lied about person 2).

User avatar
Factoids are just Datas that haven't grown up yet
Posts: 5967
Joined: Tue Nov 28, 2006 9:50 pm UTC
Location: Sydney

Re: Truth or Lie?

Postby jestingrabbit » Thu Jun 03, 2010 11:42 am UTC

Yeah, this is a repeat as suggested by redrogue, so I'm locking.
ameretrifle wrote:Magic space feudalism is therefore a viable idea.

Return to “Logic Puzzles”

Who is online

Users browsing this forum: No registered users and 9 guests