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This question already has an answer here:

The following puzzle was posted here, but providing answers to the puzzle was closed without a correct and complete answer being provided:

An inspector knows that exactly one of 3 suspects committed a crime, and interviews them to find out which. Each person lies one time, and tells the truth the other time.

A says: I did not do it. B did it.

B says: I did not do it. I know that C did it.

C says: I did not do it. B does not know who it was.

Can the inspector figure out the culprit? If so, who is it?

The original question (and answers) can be found here: Logic puzzle - 3 suspects

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marked as duplicate by Mark N, Alex, Bailey M, kaine, Engineer Toast May 12 '15 at 19:45

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • $\begingroup$ Welcome to Puzzling Bryon Jones. Unfortunately I believe there are enough 'correct' answers with solutions provided for that question although the poster has yet to accept any. The question has 'protected' answers being posted from people without more than 10 reputation. I will vote to close this question as a duplicate (as it clearly is). You will just have to be patient if you wish for an answer to be accepted in the other post $\endgroup$ – Mark N May 12 '15 at 19:10
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The correct answer is C.

Here's an accurate explanation as to why C is the correct answer:

A condition of the puzzle is that each person MUST make one statement that is false, and one that is true.

Start with suspect A: If the statement "B did it" is true, then A's other statement "I did not do it" must also be true. Since that does not meet the one true statement, one false statement condition, the statement "B did it" must be FALSE, meaning that A's statement "I did not do it" is TRUE.

On to suspect B: If the statement "I know that C did it" is true, then B's other statement "I did not do it" must also be true. Since that also does not meet the one true statement, one false statement condition, the statement "I know that C did it" must be FALSE, meaning that B's statement "I did not do it" is TRUE.

So if A and B did not do it, C did.

This perfectly harmonizes with C's statements: "I did not do it" (FALSE), and "B does not know who it was" (TRUE, as we determined that B's statement "I know that C did it" was false).

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