Safely cross the river

Question

Farmer MacDonald is taking a chicken; a pail of corn; and a large, hungry dog to market. He needs to cross a river in a very small boat that will only hold himself and one other passenger or item. He cannot leave the chicken with the corn or the chicken will eat the corn. He cannot leave the do with the chicken, because the dog will eat the chicken. How can he get them all safely across the river? How many trips will it take?

Answer 1

1. Take the chicken across first and return empty
2. Then take the dog across and return with the chicken
3. Leave the chicken and take the corn across, return empty
4. Take the chicken back across

The key is that you can't leave the chicken alone with either the dog or the corn; however, you can leave the dog and corn together.  So the chicken needs to cross the river, then cross back, then cross again.  Four trips are needed.