perplexus.info :: Liars and Knights : Who has the key?

Who has the key? (Posted on 2002-05-17)

An adventurer found a locked treasure chest in a dungeon. He tracked down three brothers (each either a Liar or a Knight) one of whom has the key to open the chest.

Each made a statement:

A: I have the key to the chest.

B: I don't have the key to the chest.

C: B Doesn't have the key.

The adventurer knows that at least one of the three is a Liar, and at least one - a Knight. Who has the key?

Submitted by levik

Rating: 2.9375 (16 votes)

Solution: (Hide)

If A had the key, he would be a Knight, but so would B and C. Since at least one of the three is a Liar, this cannot be.
If B had the key, all three turn out to be Liars, and that is also impossible, since at least one is a Knight.
Thus, it's C who has the key, making both him and B Knights, and A a Liar.

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

Subject	Author	Date
Explanation to Puzzle Answer	K Sengupta	2022-06-09 23:01:33
Puzzle Answer	K Sengupta	2022-06-08 13:34:06
Answer	Math Man	2020-03-14 21:01:43
Sol	Andre	2010-06-04 17:13:15
Solution	Praneeth	2007-08-29 02:53:24
Puzzle Solution	K Sengupta	2007-03-18 04:12:45
Solution	Chance	2006-06-01 21:17:57
Answer in the key of C...	Patrick	2005-05-13 17:34:15
Solution	Stephen Ticsay	2005-04-15 01:39:34
please ignore	FatBoy	2003-10-03 12:02:11
Solution	Lewis	2003-05-30 11:48:53
DJ,I just... ...wanted to... ...do it because... ...of so and so. OOOOOOOOOKKKKKKKKK? AGREEMENT?	Tim Axoy	2003-04-14 02:36:57
i know the answer	Jonathan	2003-03-26 06:52:41
re: The key to --	DJ	2003-03-22 17:50:35
The key to C	Tim Axoy	2003-03-22 02:33:36
aha	Hazirah	2002-08-04 00:07:08
i got it	marty	2002-05-22 22:41:50
Solution	Ender	2002-05-17 07:13:04
My Solution	TomM	2002-05-17 07:12:48

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