A man has to take a wolf, a goat, and some cabbage across a river. His rowboat can only hold the man plus either the wolf, the goat, or the cabbage. If he takes the cabbage with him, the wolf will eat the goat. If he takes the wolf, the goat will eat the cabbage. Only when the man is present are the goat and the cabbage safe from their enemies. All the same the man carries wolf, goat, and cabbage across the river. How?

Have your students try to solve this old 8th century logic problem.
Here is the answer:

1. He takes the goat across and leaves him on the other side
2. He then takes the cabbage across and leaves it on the other side, but brings the goat back with him
3. He leaves the goat on the first side and takes the wolf.
4. He leaves the wolf with the cabbage and goes back for the goat.