08 Apr '04 18:06

First of all, Hi! I'm new to RHC and am very excited to have found such a great group of people. I look forward to meeting as many of you as I can in here or on the other side of a board.

The four hats puzzle really needs to be drawn on a piece of paper to understand it, but I will try. I haven't read all the threads in this forum so I hope this has not already been mentioned.

There are four people, a wall, 2 red hats, and two blue hats.

Three people are placed on one side of the wall in a line perpendicular to and facing the wall. They are not allowed to turn around. One person is placed on the other side of the wall. Noone can see through the wall. So it looks like this:

Illustration:

Man1 Man2 Man3 Wall Man4

Man1 can see Man2 and Man3, but not Man4(on the other side of the wall)

Man2 can see Man3, but not Man1 (because he's facing the wall) or Man4

Man3 cannot see anyone.(only the wall)

Man4 cannot see anyone.(only the wall)

You place the red hats on Man1 and Man3. You place the blue hats on Man2 and Man4. Nobody can see their own hat color, only the hats of the people in front of them. Again they are all facing the wall, not allowed to move and not allowed to turn around. So now it looks like this:

Illustration:

Man1(RedHat) Man2(BlueHat) Man3(RedHat) Wall Man4(BlueHat)

You say On you're heads I put a hat. There are two red hats and two blue hats. If you know what color your hat is, speak up? After 15 seconds, one person says I know. He did.

Who was it and how did he know?

I did this with my students once. It was fun.

The four hats puzzle really needs to be drawn on a piece of paper to understand it, but I will try. I haven't read all the threads in this forum so I hope this has not already been mentioned.

There are four people, a wall, 2 red hats, and two blue hats.

Three people are placed on one side of the wall in a line perpendicular to and facing the wall. They are not allowed to turn around. One person is placed on the other side of the wall. Noone can see through the wall. So it looks like this:

Illustration:

Man1 Man2 Man3 Wall Man4

Man1 can see Man2 and Man3, but not Man4(on the other side of the wall)

Man2 can see Man3, but not Man1 (because he's facing the wall) or Man4

Man3 cannot see anyone.(only the wall)

Man4 cannot see anyone.(only the wall)

You place the red hats on Man1 and Man3. You place the blue hats on Man2 and Man4. Nobody can see their own hat color, only the hats of the people in front of them. Again they are all facing the wall, not allowed to move and not allowed to turn around. So now it looks like this:

Illustration:

Man1(RedHat) Man2(BlueHat) Man3(RedHat) Wall Man4(BlueHat)

You say On you're heads I put a hat. There are two red hats and two blue hats. If you know what color your hat is, speak up? After 15 seconds, one person says I know. He did.

Who was it and how did he know?

I did this with my students once. It was fun.