A FARMER MUST CARRY HIS DOG, A DUCK, AND A BAG OF CORN ACROSS A RIVER. THE
boat he has is very small. He can only take one of the three things in the
boat with him at one time. If he leaves the dog alone with the duck, the
dog will kill the duck. If he leaves the duck alone with the corn, the duck
will eat the corn. What is the fewest number of trips that the farmer must
make to carry all three things across the river safely?
It might be easier to keep track of this one if you draw some
diagrams, or even use stones, coins, or some kind of marker to represent
the animals