[Guest]

Hi,

I got this question from friend and i don't know the solution for this (And i don't think there is any rule saying that - you should not post the puzzles for which you don't know the answers). If someone can answer this puzzle, would be helpful

The puzzle is:

There are 4 persons in a room excluding you. Out of which 2 persons always tell truth and 2 persons always lies. And every single person knows the behaviors of other 3 persons (I mean he knows which person tells what, either truth or lie). And everyone will give you only YES/NO answers. So you should ask questions in a manner that they can answer it either YES or NO

You can ask maximum of 2 questions and after asking the 2 questions, you should determine which persons are telling truth and who all are telling lies.

FYI, i am again mentioning that i don't know the solution for this.

Thanks

Shravan

[Guest]

I might be wrong again but i think this is kind of impossible because there are only 4 possible combos based on the OP with whic u should determine which of 6 situatiosn it is. BUT if the OP actually allows you to, you can simply solve this with a paradox. lets say you ask person person A "if i ask person a and b this question will they both say the same thing?". in the case they are both truthers, they shall say yes. if they are both liars, they will keep quiet because no matter what they say, at least one of them will be telling the truth. if one is a liar and one a truther the truther will say no and the liar yes. then ask the same thing of C concerning A and C. if c is quiet, then A and C are liars. if C says yes, then A and B are truthers. If A was quiet in the first place then he and B are liars. IF A says no then C says yes, C and B are liars. I know this is even more confusing but its basically possible because there are now 3 possible responses.

QED!!!!

I dont understand why the person A will be silent in case A & B are liars and you ask the question to A. Ideally, as both tells the same thing the answer is YES. But as he is the one who always tells lies, A says NO. But i dont think A will be silent in any case. Am i missing something of your logic???

[Guest]

So far I've been able to:

1) I can discern what a target is by asking person A:

Would person B say you tell the truth?

This is basically equivilent to A xor B xor A. If A answers NO, that means person B is a liar. if A answers YES, it means that person B tells the truth.

A       B    Answer

LIES  LIES   B would say YES, so A lies and says NO

LIES  TRUE   B would say NO, so A lies and says YES

TRUTH LIES   B would say NO, so A truthfully says NO

TRUTH TRUTH  B would say YES, so A truthfully says YES.

OK. I've also figured out how to tell what the person you are asking is: Ask person A: Would BOTH B and C say you tell the truth. If the answer is YES, person A is a liar. If the answer is NO, person A tells the truth. This only works, because we are able to remove the cases which have three liars or three truth tellers (since they are not possible)

A       B     C        Answer

LIES  LIES   TRUTH     B would say YES, C would say NO,  both B&C say do NOT say YES, A lies and says YES

LIES TRUTH   LIES      B would say NO,  C would say YES, both B&C say do not say YES, A lies and says YES

LIES TRUTH   TRUTH     B says NO, C would C NO, both B&C do not say YES, A lies and says YES

TRUTH LIES   LIES      B says NO, C says NO, both B&c do not say YES, A truthfully says NO

TRUTH LIES   TRUTH     B says NO, C says YES, both b & c do not say yes, A truthfully says NO

TRUTH TRUTH  LIES      B says YES, C says NO, both B&C do not say Yes, A truthfully says NO.

What I cannot quite get is how to distinguish the third case without another question. You can get from 6 to 3 in one question, but I don't see how you can split the remaining cases (if A lies, for B C: LIE TRUTH, TRUTH LIE, TRUTH TRUTH; if A tells the truth: LIE LIE, LIE TRUTH, TRUTH LIE) with only one question that has a binary answer...

[Guest]

I dont understand why the person A will be silent in case A & B are liars and you ask the question to A. Ideally, as both tells the same thing the answer is YES. But as he is the one who always tells lies, A says NO. But i dont think A will be silent in any case. Am i missing something of your logic???

actually look at my correction. but in this case if A and B are both liars, they will answer any question the same if they both say yes then they are both telling the truth but if they both say no then they are still telling the truth the way the question is posed. they would have no choice but to keep silent.

just look at my spoiler for EUREKA! then at my spoiler for correction and there is the answer to the riddle. if you need clarification, just ask.