Puzzles
Alcuin's Snail, Invited to Lunch a League Away
A snail is invited by a swallow to lunch at a spot exactly one league away. There's just one problem: the snail can crawl no faster than one inch a day. Alcuin of York posed this to sharpen young scholars' patience with units as much as arithmetic. How long does the snail take to arrive?
Reveal the answer
With 1 league = 1,500 paces, 1 pace = 5 feet, 1 foot = 12 inches, and a 365-day year, the snail crawls 90,000 inches total, arriving after 246 years and 210 days. It's problem 1 in Alcuin of York's Propositiones ad Acuendos Juvenes (c. 800 CE), one of the earliest surviving collections of recreational math in the West.
— Alcuin of York, Propositiones ad Acuendos Juvenes — Problem 1, "Propositio de Limace," c. 800 CE