After blindfolding them, Paul picks up the five red discs, sticks one on the forehead of each logician, and hides the other discs elsewhere. After removing the blindfolds, everyone sees the discs (all red) on the others' foreheads but not the one on his own.

After a few minutes, one of the logicians (that reasons a little faster than the others) correctly states the color of his disc. How does he work it out?

Tk you. This is indeed a very hard one to be solved. Thereīs anothers similars, not posted by me, more easy than this. Try, for example, "The prime perimeter". Itīs a very nice piece of reasoning, too. 

Posted by pcbouhid on 2005-10-02 17:39:33