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?

Carl is a liar.

 

ask Carl "Is Adam a Knight?" 

Yes implies Adam is true/false knave, Bert is knight.

No implies Adam is knight, Bert is true/false knave.

Posted by Andre on 2010-06-01 18:31:57