Wolf, Goat and Cabbage problem
Here is a classic problem which people have enjoyed solving since at least the eighth century!
A man has to take a wolf, a goat and a cabbage across a river. His only problem is that he can only fit himself and either the wolf, the goat or the cabbage into his boat with him each time he crosses. If he ever leaves the wolf alone with the goat, the wolf will eat the goat. If he ever leaves the goat alone with the cabbage, the goat will eat the cabbage.
He manages to cross the river taking all three to the other side. How does he manage it?