Lost in the woods, you finally happen upon a rickety old bridge across a deep ravine. The ravine is too steep to go down and climb back up. You need to know if the bridge is safe. As 'luck' would have it, you recognize that on the other side of the bridge is that dreadful town, "Knight-and-Liarville". Everyone who lives there is a knight (who always tells the truth) or a liar (who always lies). You are tired and you've been lost in Knight-and-Liarville before. You see three men on the other side of the bridge.

You shout out: "Are you a knight?"

The first man says something, but you can't hear what he said.

The second man shouts, "He said he was a knight."

The third man shouts, "No, he didn't. He said he was a liar."

Which man do you ask to find out whether or not the bridge is safe?

(In reply to Only 1 is safe to ask... by Brian Wainscott)

Brian Wainscott: "Everyone seems to be assuming that the first person actually answered the question as asked."

Which is like assuming you can actually slide those quarters in Gamer's "Moving Quarters" puzzle. (Everyone seems to be assuming those quarters aren't actually cemented to the table.) It is reasonable to assume the first man answered the question he was asked. These puzzles and their answers must meet minimum standards of common sense; otherwise "Cannot be determined" would have to be the standard answer to every puzzle.  If the first person had answered by naming the color of his shoes, he would have been a Madman, rather than a Knight or a Liar. "My shoes are blue" is not a lie, but it is not a truthful answer to "Are you a Knight ?" 

 

 

 

 

 

 

 

 

 

Edited on March 26, 2004, 5:48 pm

Posted by Penny on 2004-03-26 17:16:06