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?
This answer assumes that there is only one person who is a knight based
on the fact that the word "man" is used in the question (it is singular
suggesting there is only one knight). Like all Liars and Knights
problems, a good strategy is to find out who is (or are) the knight(s)
in the problem and then derive the liars (and knaves if that applies).
First, we do not know what the first man said, but if he said something
true then he would be a knight. Thus, the second man would be a
knight and the third would be a liar. That is impossible from my
interpretations.
And, if the second man is a knight, then the first man is a
knight. That is impossible because there cannot be two knights
(from my interpretation again).
However, if the third is a knight, than the first is a liar (by the third man's statement) and the second man is liar too.
Thus, it would be safe to ask the the third man.
maybe...
