Some of us would have heard of this one or something similar before;
A farmer has a bag of chook food, a chook and a fox which he needs to get to the opposite side of a river. He can only take one item at a time across in his boat. For obvious reasons he cannot leave certain items on any side of the river together, i.e., the chook and chook food, the chook and the fox. How does he get all three items to the other side of the river?