Men and (Were)Wolves II

Logic Level 2

One night, you are in a room, where you are able to observe four people through a one-way mirror. Suddenly, a voice comes on over a speaker in the ceiling.

The voice says "If you can find which one among you is the werewolf, I will let the three humans go. If not, the werewolf will kill all of you in an hour."

You know that the three humans will always tell the truth, as they want to get out. Conversely, the werewolf will always lie, as they are hungry and don't want to miss an easy meal.

Person A says "Either B or D is a werewolf."
Person B says "I see somebody watching us in the next room."
Person C says "Nonsense. There are only four of us here."
Person D says "I know C isn't lying."
You want to help the three people, but you don't know who is the werewolf. Figure out who the werewolf is.

A B C D It is impossible to answer this question.

Antimatter Bee by Antimatter Bee , 16, USA

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5 solutions

Antimatter Bee
Nov 26, 2020

B must be the werewolf because it is a one-way mirror. Since you are not in the room with them, C is truthful in stating that there are only four people, also being unaware of your existence in a separate room. Because C is truthful, D must also be truthful, as they state that C is not lying. And finally, since B is the werewolf, A is truthful in their statement as well.

2 Helpful 1 Interesting 1 Brilliant 1 Confused
Hongqi Wang
Nov 28, 2020

Person A says "Either B or D is a werewolf."

if A tells truth, then B or D is werewolf; if A lies, then both B and D are human and A is werewolf. So one of A, B and D must be wolfman. And C must be human, that implies B are werewolf. D tells truth too and must be human of course.

1 Helpful 0 Interesting 0 Brilliant 1 Confused
Saya Suka
Feb 8, 2021

B & C are directly confrontational, thus one of them must be the werewolf. A & D are definitely humans, and we can use either of their statements to point out werewolf B.

0 Helpful 0 Interesting 0 Brilliant 0 Confused
Rohit Shukla
Dec 10, 2020

B must be the werewolf because it is a one-way mirror. Since you are not in the room with them, C is truthful in stating that there are only four people, also being unaware of your existence in a separate room. Because C is truthful, D must also be truthful, as they state that C is not lying. And finally, since B is the werewolf, A is truthful in their statement as well.

0 Helpful 0 Interesting 0 Brilliant 0 Confused
Richard Desper
Dec 9, 2020

C disagrees with B, which means one of those two is the werewolf. And that means that A is not the werewolf. A says that the werewolf must be B or D. So A clears C, and B is the werewolf. And we can note that D's statement is consistent with both C and D being non-werewolves.

We don't have to directly evaluate the truth value of B's statement.

0 Helpful 0 Interesting 0 Brilliant 0 Confused

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