A man is traveling with a fox, a duck, and some corn. He comes to a river with a boat and must cross it, however, he can only take one thing at a time with him in the boat. He can’t leave the fox with the duck or the duck with the corn, how does he cross the river?
The fox will eat the duck and the duck will eat the corn, but the fox won't eat the corn.
On the first trip, he takes the duck across the river and leaves it.
He then goes back across the river and brings the fox. He puts the duck back into the boat and takes it back to the other side of the river.
He then puts the corn in the boat and takes it to the side with the fox.
He gets back into the boat and brings the duck back over.