This is one of those classic river-crossing conundrums which typically has only one answer. Yet, as with so many group initiatives, the value is found in the journey and not so much the destination.
Oh, and don’t think too hard about the circumstances – it’s hypothetical, and is designed simply to stimulate critical-thinking. That is to say, don’t ask why, it’s not real.
Given the discussion and critical-thinking required, I like to form lots of small groups of 2 to 5 people to tackle this puzzle.
In your set-up, either ask your group to imagine five primary elements – a woman, a rowboat, a chicken, a fox and a bag of corn – or provide some form of prop or toy to represent each.
Explain that the woman has a dilemma – she needs to get the fox, the chicken and the bag of corn across to the other side of a river in as few moves as possible. She has a rowboat, but it can only carry her and one other item at a time.
Her dilemma is clear – she can not leave the fox and the chicken alone together (the fox will eat the chicken,) and she can not leave the chicken with the corn (the chicken will eat the corn.)
So, challenge your group(s) to identify a solution that gets all five elements safely to the other side of the river. How does the woman do it?
Allow ample time for your groups to discuss their ideas and perform lots of experiments.
Okay, here’s the solution:
To begin, the woman and the chicken cross the river together. The fox and corn are safe together.
Once on the other side, the woman leaves the chicken and returns to the fox and corn. She takes the fox across the river, and since she can’t leave the fox and chicken together, she brings the chicken back with her (that’s the trick which many groups do not think of.)
She can not leave the chicken with the corn, so she leaves the chicken and rows the corn across the river and leaves it with the fox.
Finally, she returns to pick up the chicken and rows across the river one last time. Voila!
If your groups enjoys tackling this problem, take a look at the Variations tab for three more challenging puzzles.
The key move of returning the chicken to the starting side (even though it had successfully traversed the river) may open lots of valuable discussion about the notion of taking two steps forward and one step back. Or, the notion of making decisions for the greater good.
Expect your group to (a) lament the improbability of this situation and / or (b) suggest a whole raft of innovative ways to keep the fox away from the chicken and the chicken away from the corn (eg fences, sealing the bag, etc.) Applaud their creativity and encourage them to find a solution, as hypothetical as it is.
This is interesting and i will use it very soon!