The fox, goose and bag of beans puzzle is a mental puzzle originating from an old riddle.

The story

The story tells of a farmer who is coming home from the market one day, to find himself at a river. At the market he has bought a fox, a goose, and a bag of beans. He must cross the river with these goods, however the boat he has can only contain himself and one of these items. If left alone, the fox will eat the goose or the goose will eat the bag of beans. The challenge is to get himself and the goods across the river with all three items intact.

Solution

The first step must be to bring the goose across the river, as any other will result in the goose or the beans being eaten. When the farmer returns to the original side, he has the choice of bringing either the fox or the beans across. If he brings the fox across, he must then return to bring the beans over, resulting in the fox eating the goose. If he brings the beans across, he will need to return to get the fox, resulting in the beans being eaten. Here he has a dilemma, solved by bringing the fox over and the goose back again. Now he can bring the beans over, leaving the goose, and finally returning to fetch the goose.

His actions in the solution are summarised in the following steps:

1. Bring goose over
2. Return
3. Bring fox over
4. Bring goose back
5. Bring beans over
6. Return
7. Bring goose over

Variations

Many variations exist of the three objects (eg. ducks, sacks of corn), but the central logic remains the same, being A eats B and B eats C.