WIY- I am impressed! Did you kow it beforehand or u really figured it out:)
Here is another one (not sure if it was posted alrady)
You have 3 canniballs and 3 whitemen that have to cross a river. They have one boat that can hold 2 ppl.
How is it that they can all get across (don’t forget that s/o has to bring the boat back) but at any time on either side there can’t be more cannibals than whitemen?