perplexus.info :: Liars and Knights : The three friends

The three friends (Posted on 2002-06-11)

There were once three friends. Abe is a Knight, Bill is a Liar, and Carl is neither, having been brought up in a foreign country. (This means he can either lie or tell the truth depending on what he feels like.)

One day, the three were sitting on a bench when the king's herald stopped by to deliver a message to one of them.

He asked the man sitting on the left side of the bench:

"Who's that sitting in the middle? To which the man replied: "Why that's Abe".

He then asked the man in the middle directly:

"What's your name?" and got the answer "My name's Carl."

Confused, he asked the man on the right:

"Who is that sitting in the middle?" and was immediately told: "That's Bill, of course!"

Can you help the king's herald figure out who is who?

Submitted by levik

Rating: 2.7368 (19 votes)

Solution: (Hide)

The man in the middle cannot be Abe, since Abe, being a Knight, would just tell the herald who he is, instead of claiming to be Carl.
That means that Abe is one of the other men on the bench, either to the left of the middle, or to the right of it. But the man on the left told the herald that the middle man is Abe, so he cannot be a Knight. That leaves the man on the right, who must be Abe.
Which means that the man in the middle is Bill, since Abe told the truth.
Carl then must be the man sitting on the left side, and he has decided to lie about his name in this case.

Comments: ( You must be logged in to post comments.)

Subject	Author	Date
Honest Abe	Math Man	2012-08-23 10:33:50
Sol	Andre	2010-06-04 17:18:53
Puzzle Solution	K Sengupta	2008-05-14 16:16:24
Answer	K Sengupta	2008-05-12 16:17:15
Answer	Praneeth	2007-08-29 02:58:44
Why it's ...	Lawrence	2003-08-30 21:44:50
answer	hemalatha	2003-06-10 01:07:56
Easy Solution	Lewis	2003-05-30 11:54:59
Part 1,Who sits where	Tim Axoy	2003-03-27 02:47:40
The three friends,Part 1,Seat labels	Tim Axoy	2003-03-23 04:35:28
Even shorter answer	Ender	2002-06-12 04:12:40
Direct Answer	TomM	2002-06-11 13:32:05
Answer	Happy	2002-06-11 12:48:26

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