The Farmer's Ferry
A farmer needs to cross a river with a fox, a chicken, and a bag of cornmeal. He has a small boat that can only carry himself and one item at a time.
If left alone together on either bank without the farmer present:
The fox will eat the chicken.
The chicken will eat the cornmeal.
How can he get everything safely to the other side?
Take the chicken across to the far bank (leaves fox and cornmeal together on the near bank—safe).
Return empty-handed to the near bank.
Take the fox across to the far bank.
Bring the chicken back to the near bank (leaves the fox alone on the far bank—safe).
Take the cornmeal across to the far bank (leaves fox and cornmeal together on the far bank—safe).
Return empty-handed to the near bank (leaves the chicken alone on the near bank).
Take the chicken across to the far bank.