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I don't know. (Posted on 2006-02-16) Difficulty: 2 of 5
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.)
Words are all important | Comment 24 of 52 |
Possibly some over-analysis and too many self-imposed assumptions going on here.

1) C cannot be a Knight (given)
2) C CAN be a truth first Knave - not guiilty, but knows who did it.  Remeber that eyewitnesses have been known to deny what they have seen just to protect thier own safety.  Also, he may have just oveheard a conversation, and not be involved in the planning or commission in any way.  That does not make him an accessory.   That requires a specific act, not an omission.
3) C CAN be a liar - then he did it.

Als0, I disagree with Penny - as I noted in an earlier post - the evidence "suggests" a single perp - this is at best a "maybe" in logical terms, and may be the real red herring here.

I still think that some of the multiple answers will be discounted by a sufficient analysis that involves why the problem also states that each suspect heard the answers in a spcific order.  Just havn't figured it out yet.


  Posted by Kenny M on 2006-02-17 21:05:19
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