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 I don't know. (Posted on 2006-02-16)
ou are a logician in training for the police, and the time has come to take the certification test. The police chief brings you the test one morning, and says, "I must warn you, this is your only chance at the certification test; If you fail, you must keep training for another year before you can take it again."

- Five suspects were interrogated for a bank robbery.

- Each suspect was either a knight, a knave, or a liar.

- Knights always tell the truth.

- Liars always lie.

- Knaves strictly alternate truths and lies with each statement.

- Police have evidence that suggests the perpetrator acted alone.

- Police have evidence that suggests the perpetrator acted alone.

>During the interrogation, two questions were asked (consecutively) of each of the five suspects. Each suspect heard the other suspects' responses, and none of them made a statement between his or her two answers. Here are the two questions and their responses.

"Did you rob the bank?"
A: No.
B: No.
C: No.
D: Yes.
E: Yes.

"Who robbed the bank?"
A: E.
B: A.
C: l don't know.
D: E.
E: A.

The interrogators mentioned that something about their statements didn't seem quite right. The police chief adds, "The only hints I can give you are that C is not a knight and that there is only one correct answer. I'll be back in 24 hours to ask you who robbed the bank."

 No Solution Yet Submitted by Dustin Rating: 3.3333 (6 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
 re(5): Insoluble | Comment 23 of 52 |
(In reply to re(4): Insoluble by AvalonXQ)

When the police say that someone "acted alone", they don't just mean he was alone during the actual bank robbery. They mean he acted without any accomplices.

If someone other than C robbed the bank, and C then lies to the police and says he doesn't know who did it, to shield the perpetrator, then he is obviously an accomplice / accessory, and the robber didn't "act alone" (in police parlance) even if he was physically alone during the commission of the crime.

The puzzle explicitly states this: "Police have evidence that suggests the perpetrator acted alone."

But maybe I'm overanalyzing a puzzle. I've been known to do that.

 Posted by Penny on 2006-02-17 19:52:56

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