Four pairs of lords and ladies all went to a royal ball. Each lord was wearing one color (yellow, red, blue, or green) and each lady was also wearing one of these colors. No couple was wearing the same color, so it was hard to tell who was married to who.

Using the clues, can you determine which lord is with which lady?

1. The Green Lord is with the Red Lady, if and only if the Yellow Lord is with the Blue Lady.

2. The Yellow Lord is with the Red Lady if and only if the Green Lord is with the Yellow Lady

3. The Red Lord is with the Blue Lady, if and only if the Green Lord is with the Red Lady.

In this kind of problems, hints are always false, so:

From 1, the Yellow Lord mustn't be with the Blue Lady, and from 2, he isn't with the Red Lady either; as he cannot be with the Yellow Lady, therefore the Yellow Lord is with the Green Lady.

From 1, the Green Lord isn't with the Red Lady, and from 2, he isn't with the Yellow Lady either; as he cannot be with the Green Lady, the Green Lord is with the Blue Lady.

From 3, the Red Lord isn't with the Blue Lady, and as he cannot be with the Green Lady (she is with another) or with the Red Lady, the Red Lord is with the Yellow Lady.

Finally, the only possible pairing is that the Blue Lord is with the Red Lady.

DONE!!

PS. To finish, remove tongue from cheek...
Edited on April 25, 2004, 7:18 pm

Posted by Federico Kereki on 2004-04-25 18:56:53