GAME: MindTrap

Murder by logic

Professor Z was killed by one of his four students, who was helped by another of the four. His students declared:

A: If B is guilty of something, then C must be innocent.
B: If A is innocent, then C must be guilty.
C: If B was the killer, then D must have had nothing to do with the crime.
D: I am innocent.


As everybody should know, guilty parties always lie, and innocent people always tell the truth. Who killed the professor, and who was his accomplice?


__________
D's declaration is worthless: were he innocent or guilty he could have said so.


Suppose C was guilty: as he would lie, then B should be the killer, but D would have to be involved too, making three guilty parties; it follows that C was innocent.

Suppose B was innocent: A could be innocent or guilty. If A was innocent, then C would have to be guilty, but we showed C was innocent, so A couldn't be innocent. If A was guilty, since he lied, B and C must have been guilty -- and that's contradictory. As A cannot be either guilty or innocent, B cannot be innocent; he is guilty.

Since B is guilty, A must be innocent, and C must be too (which we had already proved). We have now that B and D are guilty, but if B was the killer, then D would be innocent (as C said) so B must have been the accomplice, and D the killer.

Quote:

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Originally Posted by a d e p t

Murder by logic

Professor Z was killed by one of his four students, who was helped by another of the four. His students declared:

A: If B is guilty of something, then C must be innocent.
B: If A is innocent, then C must be guilty.
C: If B was the killer, then D must have had nothing to do with the crime.
D: I am innocent.

As everybody should know, guilty parties always lie, and innocent people always tell the truth. Who killed the professor, and who was his accomplice?

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A and D are the killers.

A is guilty so the statement "If B is guilty of something, then C must be innocent." is false. Correctly it would read "If B is guilty of something, then C must be guilty." B is not guilty, so C must not be guilty.
B is innocent so the statement "If A is innocent, then C must be guilty." is true. A is not innocent, so C must not be guilty.
C is innocent so the statement "If B was the killer, then D must have had nothing to do with the crime." is true. B was not the killer so D did have something to do with the crime.
D is guilty, so the statement "I am innocent" is false.

Not ...quite.

Quote:

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Originally Posted by a d e p t

Not ...quite.

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Not ...quite. Meaning completely and absolutly wrong! It's probably B and C then. So I just sent two innocent people to the electric chair. They would have died in seventy years or so anyway, so what's the big deal? I say lock em all up and call it good. :devil: BTW, I'm not guessing B and C here, so if I happen to be right, don't start throwing points around.

I won't. https://forums.windrivers.com/images.../2005/03/1.gif

Quote:

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Originally Posted by a d e p t

Murder by logic

Professor Z was killed by one of his four students, who was helped by another of the four. His students declared:

A: If B is guilty of something, then C must be innocent.
B: If A is innocent, then C must be guilty.
C: If B was the killer, then D must have had nothing to do with the crime.
D: I am innocent.

As everybody should know, guilty parties always lie, and innocent people always tell the truth. Who killed the professor, and who was his accomplice?

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B and A

innocent people tell the truth, so D is telling the truth (going by presence of the word innocent)

since D is innocent assume B must be guilty
Since B is guilty C must be innocent leaving A as a guilty party

Quote:

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Originally Posted by a d e p t

Murder by logic

Professor Z was killed by one of his four students, who was helped by another of the four. His students declared:

A: If B is guilty of something, then C must be innocent.
B: If A is innocent, then C must be guilty.
C: If B was the killer, then D must have had nothing to do with the crime.
D: I am innocent.

As everybody should know, guilty parties always lie, and innocent people always tell the truth. Who killed the professor, and who was his accomplice?

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B is the killer, A is the accomplice.
Because...

If C is innocent then D is innocent.
If B is guilty then C is innocent.
If A is innocent then C is guilty.
So A and B are the guilty, B is the killer making C's statement true.

Do you want the answer specific as to who is the killer and who is the accomplice?

D was the killer, and B was the accomplice.

A's statement is still correct (B is guilty, and c is innocent)

B's Statement is false (Aand C are both innocent)

C's statement is correct ( b was not the killer, so D could be involved)

D's statement was false (he was guilty).

Quote:

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Originally Posted by a d e p t

Murder by logic

Professor Z was killed by one of his four students, who was helped by another of the four. His students declared:

A: If B is guilty of something, then C must be innocent.
B: If A is innocent, then C must be guilty.
C: If B was the killer, then D must have had nothing to do with the crime.
D: I am innocent.

As everybody should know, guilty parties always lie, and innocent people always tell the truth. Who killed the professor, and who was his accomplice?

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Personally, I think that:

D is the killer (he's guilty, so he's lying)
C is the accomplice (he's trying to cover up by saying D had nothing to do with the crime)

I could be totally wrong, but you never know.

Quote:

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Originally Posted by Camaro80z

D was the killer, and B was the accomplice.

A's statement is still correct (B is guilty, and c is innocent)

B's Statement is false (Aand C are both innocent)

C's statement is correct ( b was not the killer, so D could be involved)

D's statement was false (he was guilty).

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I think you're right, I found flawed logic in mine. This question hurts my brain (and people kept calling and wanting me to work just when I was on the verge...). :devil:

Personally, I think it was a d e p t in the study with the candlestick.

I always rocked at Clue. :D

Quote:

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Originally Posted by Spork

Personally, I think it was a d e p t in the study with the candlestick.

I always rocked at Clue. :D

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No. It was NooNoo, in the Bedroom, with the Revolver!!

:devil: :devil:

Quote:

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Originally Posted by Camaro80z

D was the killer, and B was the accomplice.

A's statement is still correct (B is guilty, and c is innocent)

B's Statement is false (Aand C are both innocent)

C's statement is correct ( b was not the killer, so D could be involved)

D's statement was false (he was guilty).

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That's the correct answer.

So what's the next question?