In the city of Enigmamia every person is either a knight or a liar. One night, two robbers managed to break into the Enigmamia Central Bank.

Five men were brought to the police station for questioning. It was certain both robbers were present. To narrow the field, each man was individually interrogated about the identities of the robbers. The results were:

Alex: 1. At most one of Bill and Eddy is guilty. 2. Dave is guilty.

Bill: 1. Both Alex and Carl are guilty. 2. Eddy is not guilty.

Carl: 1. At least one of Dave and Eddy is guilty. 2. Bill is not guilty.

Dave: 1. Exactly one of Alex and Bill is guilty. 2. Carl is guilty.

Eddy: 1. Neither Carl nor Dave is guilty. 2. Alex is guilty.

Which two suspects robbed the bank?

Bill has to be a liar. He said that Alex and Carl were both guilty - if this was true then Carl's first statement would be a lie, so he would be a liar, and because of his second statement that would also make Bill guilty.

We now know that Eddy is guilty, although one out of Alex and Carl can still be guilty.

Because we know Eddy is guilty we know that Carl is a knight, because of his 1st statement. That menas Bill is not guilty.

Dave is a liar. If he was a knight, there would have to be three guilty people. Obviously, in his 1st statement they can't both be guilty, so neither Alex nor Bill is guilty (but we already new about Bill).

The second robber is either Carl or Dave. Since neither Alex nor Bill is guilty, Dave is a liar. This means that Dave is guilty.

The status of each person is:

Alex: Knight - Innocent
Bill: Liar - Innocent
Carl: Knight - Innocent
Dave: Liar - Guilty
Eddy: Liar - Guilty

Posted by Lewis on 2003-07-09 08:55:28