I am reading DUCY and the example of painting all 3 guys forehead's black or white, and the man who can explain what color is on his forehead has me baffled. Can someone explain it to me.

Pasted from a similar puzzle aI saw a few years ago but maybe the same as in the book.

Let's name them 1,2,3.
1 is the smart guy, and here is how he thinks:
1 is assumming that he has a white marker.
Now 1 will walk in 2's shoes to think:
2 now is seeing 1 white and 1 black (say 1 is white and 3 is black).In that case, 2 is smart enough to know that he's not white. Because if 2 is white and 1 is white, 3 will see 2 white markers, and he would not raise his hand. So 2 will know that he's not white . But 2 is not doing anything.
So 1 knows that 1 doesn't have a white marker as he presumed.
He has the black one.
and the fact is everyone has a black marker

The explanation is, I can see two other people who are not raising their hands and I know both can see at least one person with white painted on their head (the other guy). If I had black on my forehead they would both raise their hands because they would assume two heads are painted black and they must be the second because neither of them have done this I know my head is white.

I originally heard that riddle as knights wearing red and/or white caps. It took me two and a half hours to figure it out, lol.

Here's another one from http://*******/9m9U65:

"Many years ago in a small Indian village, a farmer had the misfortune of owing a large sum of money to a village moneylender. The moneylender, who was old and ugly, fancied the farmer's beautiful daughter. So he proposed a bargain.

He said he would forgo the farmer's debt if he could marry his daughter.
Both the farmer and his daughter were horrified by the proposal. So the cunning money-lender suggested that they let providence decide the matter.

He told them that he would put a black pebble and a white pebble into an empty money bag. Then the girl would have to pick one pebble from the bag.

1) If she picked the black pebble, she would become his wife and her father's debt would be forgiven.
2) If she picked the white pebble she need not marry him and her father's debt would still be forgiven.
3) But if she refused to pick a pebble, her father would be thrown into jail.

They were standing on a pebble strewn path in the farmers field. As they talked, the moneylender bent over to pick up two pebbles. As he picked them up, the sharp-eyed girl noticed that he had picked up two black pebbles and put them into the bag. He then asked the girl to pick a pebble from the bag.

Now, imagine that you were standing in the field. What would you have done if you were the girl? If you had to advise her, what would you have told her?

Careful analysis would produce three possibilities:

1. The girl should refuse to take a pebble.
2. The girl should show that there were two black pebbles in the bag and expose the money-lender as a cheat.
3. The girl should pick a black pebble and sacrifice herself in order to save her father from his debt and imprisonment.

Take a moment to ponder over the story. The above story is used with the hope that it will make us appreciate the difference between lateral and logical thinking. The girl's dilemma cannot be solved with traditional logical thinking. Think of the consequences if she chooses the above logical answers.

What would you recommend to the Girl to do? Think and than proceed further."

Could she conceal a white pebble in her hand and then pretend to pick it out of the bag? That way the money lender would have to decide to expose himself as a fraud.

The girl should pick a pebble from the bag and immediately swallow it. Then she will ask the bag to be emptied by the moneylender to reveal that there is only one black pebble left (thus she picked the white one.)

She could ask the money lender to pick a pebble, stating that she'd have the other pebble?

Anything that doesn't result in a single black pebble being shown besides refusing. She could pick it and drop it to the ground before it's seen.

TwoThirtyTwo, grats, u're correct!

However, aceinspace gets bonus points for suggesting eating the pebble.