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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.)
re: Insoluble | Comment 12 of 52 |
(In reply to Insoluble by AvalonXQ)

In solution 1, C, a knave, is telling two consecutive truths, since the puzzle states that the perpetrator "acted alone", implying that C will only know who the perpetrator is, if C himself is the perpetrator. [Allowing C to be a passive witness of another suspect's crime is an unwarranted addition to the bare assumptions of the puzzle. The perpetrator "acted alone".]

Solutions 2, 4 and 5 have the same problem.

In solution 3,  C, a knave, tells two consecutive lies, since C did it and must be aware that he did it.


  Posted by Penny on 2006-02-17 08:24:30
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