I've found this somewhere on the World Wide Web and I can tell you that is a very good one but I'm sure there are some really smart BHatters here who can find the correct answer. Anyway, I will put the answer in a .jpg at the end of this post for those lazy thinkers who just want to find out the answer without a hassle. For the rest of you, Knock yourselves out guys ! A leader of a country decides to free a political prisoner in honour of his birthday. After looking through all the prisoners, they had short-listed it to three prisoners who seemed all equal. He decided to give the prisoners a puzzle to work out, the first person to get the correct answer AND explain how he got it, would go free. If he incorrectly guessed at the answer, or used faulty logic to get the answer, then he got an additional THREE years added to his sentence. So he must be really sure of his answer and his logic to get free. He led the prisoners down to a dark dungeon that was lighted by a single light bulb. There were no mirrors or windows in the dungeon. He showed them a bag in which he had put 3 WHITE and 2 BLACK disks. The prisoners saw all 5 disks. He then had them take their shirts off, and on their bare backs he secretly attached one of the disks on each of the three prisoners. The disks were put in a place where none of the prisoners could see the colour of the disk on his own back, but could see the colour of the disk on the other two prisoners' backs. The remaining two disks were kept in the bag and none of the prisoners were able to see what was left in the bag. In order to get released, they must be the first prisoner to get the correct answer AND explain how he got it. Remember, a false guess, or faulty logic, meant THREE more years of prison. The prisoners started to move around and look at each other's backs. Remember they could not see their own backs. Nothing happened for about 30 MINUTES, then suddenly one prisoner, let's say his name is Igor, gets an idea. He sees TWO WHITES on the backs of his fellow prisoners. He says, "Ahaha". He goes to the jail keeper, tells him his colour, and tells him the logic that lead him to deduce this colour. The jail keeper says that he is correct, and he is freed. Your mission: What colour did he have on his back, and what is the logic that lead you to that decision? Please remember, this is a logic puzzle, NOT A PROBABILITY question. You can logically get to an answer. Now, since I needed two hints to get it, I will give you the two hints as well: Pretend you are Igor, and (1) What do the other prisoners see? (remember, they can see your back), and (2) What are the other prisoners thinking. (Assume that all three prisoners are equal in intelligence). And please if you figure it out or if you look at the image don't spoil it in your comments or better, (for the ones who want to solve it by themselves) to not read the comments until you give up or think you know the right answer. Good luck !