A farmer needs tot ake his goat, wolf and cabbage across the river. His boat can only accommodate him and either his goat, wolf, or cabbage. If he takes the wolf the goat will eat the cabbage if he takes the cabbage the wolf will eat the goat only when the man is present is there arethe cabbage and goat safe from their respective predators. How does he get everything across the river?

Take the goat first, return for the fox, when he drops off the fox, take the goat back with him, drop the goat back off at the original site, take the cabbage with him, drop it off with the fox, return one more time to pick up the goat. He will need to make 4 trips across the river, and voilà!