The fox, the hen and the corn
Once upon a time a farmer went to market and bought a fox, a hen and a sack of corn.
If left together on the riverbank, the fox would eat the hen, or the hen would eat the corn.
Adults and children
Two adults and two children need to cross a river in a rowing boat. Can you determine how to get everyone across, and how many crossings are needed, given the following information?
What if there were $4$ adults and $2$ children?
- All adults weigh the same
- Each child weighs half as much as an adult
- The boat can only carry the weight of one adult
- The boat must have someone in it to row it!
What if there were $100$ adults and $2$ children?
What if there were $n$ adults and $2$ children?
If you enjoyed these problems, you may also like to take a look at Crossing the Bridge.
With thanks to Don Steward, whose ideas formed the basis of this problem.
Notes and Background
When you try to solve these 'river crossing' puzzles, you are attempting some of the same problems that were set by Alcuin, an ecclesiastic from the 9th century, for the Emperor Charlemagne.
Alcuin's version of Problem 1 concerned a wolf, a goat and a cabbage.