The following two facts are known about Adam, Bert, and Carl:

1) Of Adam, Bert, and Carl, there is one knight, one knave, and one liar.
2) Adam said once, "Bert said that Carl isn't a knight."

Can you ask one yes/no question to one person and figure out who is who? If not, how many questions must you ask?

(In reply to re(2): Two Questions by Liam)

Its interesting that you refer to bert and adam as having the same version of events.

The question doesn't say that Bert said anything at all. The question merely says that Adam said he did. So bert's "version of events" (that carl is not a knight) could be either true or false, regardless of whether adam's lied about bert's version of events, or told the truth about them. Adam merely alleged that bert said that. Maybe he did. Maybe he did not.

There is insufficient information in the question to deduce that from scratch. That's what makes it a good quesion. We cannot rule out ANY possible combination of liar, knave, and knight without more information.

Posted by Ben Gornall on 2005-02-18 09:08:07