Difficult Riddle!

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Posted 05 November 2006 - 06:56 PM

Looking at LibertÃ©'s question "Are you a liar?" how would you know that the person is telling the truth if he answers NO? I understand that if he answers YES, then he's definitely a liar, because he could be lying about the fact that he's a liar....But if he answers NO, then can't he be lying?

I'm confused...

The question I would ask the first person would be:

"If I asked the second person if they were a liar what would they say?"

If the first person is a liar then the second person is honest so the answer would be YES.
If the first person is honest then the second person is a liar so the answer would be NO.

In this way we can work out the order of the liars and honest people.

#22 Iraq11

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Posted 05 November 2006 - 07:40 PM

Wow this is becoming complicated...
Brother Iraq11, just to clarify...if there are 5 persons how come we only get to ask 4 questions?

That's the difficulty of the problem, brother freedslave. If we had 5 questions, it would have been easy! One out the 5 persons will not be asked.
And as brother hkrespect mentioned, we can ask only one question per person (total 4 questions maximum).

Salaams

coolbeans
first off, I'm assuming that we are not allowed to actually check the doors? bcaz that would make it too easy.
Now b4 I try to put my answer in boolean format, there are totall of 5 doors including the
one that M enters from?
Because If so then we have totall of 4 doors to choose from
and the format can only be
TFTF or FTFT
But if there are 6 doors then it has to be
tftft or ftftf
lemme know which condition applies b4 I go further?
Peace

We do not take what M entered from into consideration. There are 5 distinct doors apart from where he entered (using your terminology, there are 6 doors).

And still no one has solved the problem yet!!

#23 Haqqul_Yaqeen

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Posted 05 November 2006 - 08:03 PM

The question I would ask the first person would be:

"If I asked the second person if they were a liar what would they say?"

If the first person is a liar then the second person is honest so the answer would be YES.
If the first person is honest then the second person is a liar so the answer would be NO.

In this way we can work out the order of the liars and honest people.

ooooh I see...I initially misread the question...alright, that makes sense.

But this is quite a difficult riddle indeed...

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Posted 06 November 2006 - 12:10 AM

There are five people so we have 5 questions right?

In which case my method establishes whether the first person is truthful T or a liar L.

Ask the second person if D1 (door1) is the one we want, since we know if he is T or F we can either choose or eliminate this door.

Ask the third person if D2 is the one we want, since we know if he is T or F we can either choose or eliminate this door.

Ask the fourth person if D3 is the one we want, since we know if he is T or F we can either choose or eliminate this door.

Ask the fifth person if D4 is the one we want, since we know if he is T or F we can either choose or eliminate this door.

Now we have asked 5 questions and we have either gotten the right door or we have eliminated 4 of them. I don't understand why this isn't correct!

#25 Haqqul_Yaqeen

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Posted 06 November 2006 - 12:12 AM

^^cuz you're only allowed 4 questions to 4 people lol.

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Posted 06 November 2006 - 12:21 AM

^^cuz you're only allowed 4 questions to 4 people lol.

But there are 5 people in the room and we are allowed to ask one question to each!

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Posted 06 November 2006 - 12:30 AM

Fine if we can only ask 4 questions I can still do it.

Assuming my method of assertaining whether the first person is T or L to be correct.

Ask the second person if the correct door is one of D1, D2 or D3. If P1 is a liar then P2 is honest (and if P1 is honest then P2 is a liar) so depending on his answer ww will know if the door we want is one of those three or one of the other 2.

Now we either have 3 doors left to choose from or 2.

Assume we have 3 left (D1, D2 and D3). We can now use my method which could be used if we had 5 questions:

Ask the third person if D1 is the one we want, since we know if he is T or F we can either choose or eliminate this door.

Ask the fourth person if D2 is the one we want, since we know if he is T or F we can either choose or eliminate this door.

Now we have either gotten the right door or eliminated a further 2 doors, leaving the correct door! D3 in this case.

Done now?

#28 vishah

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Posted 06 November 2006 - 06:06 AM

Fine if we can only ask 4 questions I can still do it.

Assuming my method of assertaining whether the first person is T or L to be correct.

Ask the second person if the correct door is one of D1, D2 or D3. If P1 is a liar then P2 is honest (and if P1 is honest then P2 is a liar) so depending on his answer ww will know if the door we want is one of those three or one of the other 2.

Now we either have 3 doors left to choose from or 2.

Assume we have 3 left (D1, D2 and D3). We can now use my method which could be used if we had 5 questions:

Ask the third person if D1 is the one we want, since we know if he is T or F we can either choose or eliminate this door.

Ask the fourth person if D2 is the one we want, since we know if he is T or F we can either choose or eliminate this door.

Now we have either gotten the right door or eliminated a further 2 doors, leaving the correct door! D3 in this case.

Done now?

I wonder whether there is any way out hihihih B) B) sounds cool

#29 Iraq11

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Posted 06 November 2006 - 01:49 PM

Fine if we can only ask 4 questions I can still do it.

Assuming my method of assertaining whether the first person is T or L to be correct.

Ask the second person if the correct door is one of D1, D2 or D3. If P1 is a liar then P2 is honest (and if P1 is honest then P2 is a liar) so depending on his answer ww will know if the door we want is one of those three or one of the other 2.

Now we either have 3 doors left to choose from or 2.

Assume we have 3 left (D1, D2 and D3). We can now use my method which could be used if we had 5 questions:

Ask the third person if D1 is the one we want, since we know if he is T or F we can either choose or eliminate this door.

Ask the fourth person if D2 is the one we want, since we know if he is T or F we can either choose or eliminate this door.

Now we have either gotten the right door or eliminated a further 2 doors, leaving the correct door! D3 in this case.

Done now?

Done. Problem is solved!

#30 llogical

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Posted 06 November 2006 - 01:54 PM

Done. Problem is solved!

Dag, I'm too late

#31 Iraq11

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Posted 06 November 2006 - 02:06 PM

Here is another method:

For N = 1 to 4: ask person N, "will person N+1 say door N leads to Islam?"

N is the right door only if we receive "No" as an answer, you know why? Because:
1) If P(N) is truthful: then P(N+1), liar, will deny that D(N) (the right door) leads to safety so P(N) will tell us "No".
2) If P(N) is liar: then P(N+1), truthful, will confirm that D(N) (the right door) leads to safety so P(N) will lie and tell us "No".

If the answer is "No" in any of the four questions, then the corresponding door (N) leads to Islam. If no "No" response is received, then the remaining fifth door leads to Islam.

And Allah knows best.

#32 Iraq11

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Posted 06 November 2006 - 02:28 PM

I'll go further with the riddle: there is a solution to the problem using only 3 questions!!

So, bro freedslave, sis Haqqul_Yaqeen, bro hkrespect, BelinQuest, llogical, LibertÃ© or any other member: Can you solve the problem using maximum 3 questions?

#33 abd_ar_Rahmaan

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Posted 08 November 2006 - 02:06 AM

mind's tired right now, maa shaa allaah. in shaa Allaah, then be back later to try and solve if others haven't blatantly answered it.

#34 Haqqul_Yaqeen

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Posted 08 November 2006 - 03:34 AM

I couldn't solve it using 4 questions, you think I can solve it with 3? lol but LibertÃ© is good, he might.

#35 freedslave

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Posted 26 November 2006 - 03:49 PM

I'll go further with the riddle: there is a solution to the problem using only 3 questions!!

Anyone else knows the answer to this new riddle?

Well I'm stumped Iraq11...I tried it out a few days before but I couldn't get it and now I'm totally out of ideas to solve this....

#36 Iraq11

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Posted 09 December 2006 - 01:09 PM

I'll go further with the riddle: there is a solution to the problem using only 3 questions!!

It's quite a hard problem, but I'm sure IF members can solve it!!!

Anyone to try?

#37 Seri

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Posted 09 January 2007 - 07:57 AM

Akum
what about if i ask them what colour my shirt is then i will know who lies and who doesnt

#38 Muhsinmuttaqi

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Posted 03 March 2007 - 02:04 AM

Assalamu Alaykum

Maybe, order them to confront the enemies of Islam. The truthful will follow you, but the hypocrites will find an excuse not to follow you.

#39 Iraq11

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Posted 26 December 2007 - 05:24 PM

I'll go further with the riddle: there is a solution to the problem using only 3 questions!!

So, bro freedslave, sis Haqqul_Yaqeen, bro hkrespect, BelinQuest, llogical, LibertÃ© or any other member: Can you solve the problem using maximum 3 questions?

Can anyone solve the problem with maximum 3 questions?