A farmer with a wolf, a goat, and a cabbage must cross a river by boat. The boat can carry only the farmer and a single item. If left unattended together, the wolf would eat the goat, or the goat would eat the cabbage. How can they cross the river without anything being eaten?

You probably know this puzzle. There are two efficient solutions, related by a symmetry that switches the wolf and the cabbage.

But what you might *not* know is that this puzzle goes back to a book written around 800 AD, attributed to Charlemagne's advisor Alcuin! Charlemagne brought this monk from York to help set up the educational system of his empire. But Alcuin had a great fondness for logic. Nobody is sure if he wrote this book - but it's fascinating.

It has 53 logic puzzles. It's called "Propositiones ad Acuendos Juvenes", or "Problems to Sharpen the Young". If the wolf, goat and cabbage problem is too easy for you, you might like this one:

"Three men, each with a sister, must cross a boat which can carry only two people, so that a woman whose brother is not present is never left in the company of another man."

There are also trick puzzles, like this:

"A man has 300 pigs. He ordered all of them slaughtered in 3 days, but with an odd number killed each day. What number were to be killed each day?"

Wikipedia says this was given to punish unruly students - presumably students who didn't know that the sum of three odd numbers was odd.

It's fascinating to think that while Franks were fighting Saxons and Lombards, some students in more peaceful parts of the empire were solving these puzzles!

(1/n)

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This is why I really like fedi, so much interesting and thought provoking content.

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