perplexus.info :: Liars and Knights : Find the killer

Find the killer (Posted on 2016-06-20)

British puzzle creator Hubert Phillips invented this genre of puzzle in the 1930s.

I have slightly modified a puzzle attributed to H.P. (a.k.a. Caliban).

One of five people is a murderer.
Here are their statements:
Bernie: Becky didn’t do it.
Benny: Betty did it.
Bella: Becky is innocent.
Betty: Becky did it.
Becky: I did not do it.

Can you identify the killer?

Given k people, including the killer, lied – provide your answers and reasoning for all possible values of k.

See The Solution Submitted by Ady TZIDON

Rating: 5.0000 (1 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)

Even shorter solution

| Comment 3 of 5 |

I like Charlie's approach. Here is an even shorter version.

If Bernie did it, then he is telling the truth. Contradiction.

If Benny did it, then there are 2 liars.

If Bella did it, then she is telling the truth. Contradiction.

If Betty did it then there is only 1 liar.

If Becky did it then there are 4 liars.

So, there can only be 1, 2 or 4 liars, making the killer Betty, Benny or Becky, respectively.

Posted by Steve Herman on 2016-06-21 11:24:15

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