Forget the story or why this situation occurred, you can make that up yourself. Or not.

Anyway, the situation is that there are 100 prisoners in a line, and each one has on either a black hat or a white hat. Each prisoner doesn’t know the color of his own hat, but he can see the colors of the hats of everyone in front of him.

The prison wardens have arranged this situation, and they now plan to start at the back of the line and move up towards the front, asking each prisoner in turn what color his (that prisoner’s own) hat is. If he’s wrong, that prisoner will be shot on the spot.

The prisoners knew about this situation beforehand, so they devised a plan to minimize the number which could be killed. What’s the plan?

And… to head off another potential solution which I thought of (and liked, and I still think it’s the most elegant one, sorry!): the prisoners, when asked, can only say “black” or “white”. One can’t inflect his voice upwards or cough or breathe in a certain way or anything like that to communicate to the person in front of him what color his hat is.

Thanks again, Vicky, for sharing this one, too!

And John, I already thought of the answer (figured it out myself, thank you very much), so don’t worry about spoiling it for me, at least. But if you thought of it, please don’t post it on the board for a few days. You can email me directly if you want.