Fox, goose and bag of beans puzzle
The fox, goose and bag of beans puzzle is a river crossing puzzle. It dates back to at least the 9th century, and has entered the folklore of a number of ethnic groups.
Once upon a time a farmer went to a market and purchased a fox, a goose, and a bag of beans. On his way home, the farmer came to the bank of a river and rented a boat. But in crossing the river by boat, the farmer could carry only himself and a single one of his purchases: the fox, the goose, or the bag of beans.
If left unattended together, the fox would eat the goose, or the goose would eat the beans.
The farmer's challenge was to carry himself and his purchases to the far bank of the river, leaving each purchase intact. How did he do it?
The first step must be to take 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 taking either the fox or the beans across next. If he takes the fox across, he would have to return to get the beans, resulting in the fox eating the goose. If he takes the beans across second, he will need to return to get the fox, resulting in the beans being eaten by the goose. The dilemma is solved by taking the fox (or the beans) over and bringing the goose back. Now he can take the beans (or the fox) over, and finally return to fetch the goose.
His actions in the solution are summarised in the following steps:
Thus there are seven crossings, four forward and three back.
The puzzle is one of a number of river crossing puzzles, where the object is to move a set of items across a river subject to various restrictions.
In the earliest known occurrence of this problem, in the medieval manuscript Propositiones ad Acuendos Juvenes, the three objects are a wolf, a goat, and a cabbage. Other cosmetic variations of the puzzle also exist, such as: wolf, sheep, and cabbage;, p. 26 fox, chicken, and grain; fox, goose and corn; and panther, pig, and porridge. The logic of the puzzle, in which there are three objects, A, B, and C, such that neither A and B nor B and C can be left together, remains the same.
The puzzle has been found in the folklore of African-Americans, Cameroon, the Cape Verde Islands, Denmark, Ethiopia, Ghana, Italy, Romania, Russia, Scotland, the Sudan, Uganda, Zambia, and Zimbabwe., pp. 26–27; It has been given the index number H506.3 in Stith Thompson's motif index of folk literature, and is ATU 1579 in the Aarne–Thompson classification system.
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