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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.)
Solution A potential answer | Comment 28 of 52 |
(In reply to No Subject by AvalonXQ)

Disregard the evidence that "suggests" they acted alone, and I have a solution.
B and C acted together to complete the robbery.  The one correct answer is A's, when he says he didn't commit the robbery.
A can't have commited the robbery, because A is listed as an answer twice, and since only one answer is correct, they both must be wrong.  This means that A's first answer is correct, which means all of the other answers are wrong.  Thus B and C lied when they said they didn't rob the bank.  All the other answers check out this way, and this makes C a liar rather than a knight.

  Posted by AvalonXQ on 2006-02-18 18:52:13

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