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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.)
Some Thoughts maybe "I dont know" | Comment 42 of 52 |
(In reply to Compilation of oddities in this problem: by Avin)


As has been mentioned numerous times already..  this can't be solved so that there is just one culprit.
Also.. if there is just one culprit who acted alone, the other 4 suspects wouldn't know the identity of the culprit... so it wouldnt matter who are liars, knights, or knaves..   anyone who isn't a robber would be guessing when asked "who robbed the bank"

The problem states there are 5 suspects, and 1 robber. Nowhere though does the problem state that the chief knows that one of the suspects is in fact the robber.

 I submit that none of the suspects are guilty.

Also.. the chief says at the end "..there is only one correct answer, I'll be back in 24 hours to ask you who robbed the bank"

'One correct answer' might not apply directly to the question " who robbed the bank"
 Maybe the police chief meant...  " When I come back in 24 hours, there is only 1 correct answer, you the logician in training, can give me, the chief of police?"
And you, the logician in training, your answer would be 
"I don't know"

Either that or his answer should be "None of these are the robber"

Edited on March 6, 2006, 4:52 pm
  Posted by Highway6 on 2006-03-06 16:47:46

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