Mr. Jauris told us this riddle at a lecture of logics. I find it very elegant.
Three Chinamen
There are three Chinese guys sleeping in a hotel room. Someone paints their faces with black color during the night. When they wake up in the morning they look at each other and all start laughing.
If one of them realizes he is black too he stops laughing. Because they are all smart and they know it about each other one of them will realize it soon. How did he find out?
Just realize that if two friends are dirty it means that I am too. If I see two laughing dirty guys it doesn’t mean that I’m dirty too they might be laughing at each other and I might be clean. Chinese didn’t point or say anything.
Hint
Important information is that they know about each other that they are smart. They can assume from the fact that his friends didn’t realize something yet.
Answer
I’m looking at two laughing black Chinese. If I was dirty they must realize that they’re dirty. They would both see that I’m clean so they’re laughing at each other. If they didn’t realize this and are still laughing it has to mean that I’m dirty too.
