Alcuin's Hound and Hare
A hare stands at one end of a 150-foot field; a hound stands at the other and gives chase. Each leap of the hound covers 9 feet; each leap of the hare covers only 7 feet. Leaping at the same rate, with the hare unable to turn aside, how many leaps does it take the hound to catch the hare — and how many feet will the hound have covered by then?
Reveal the answer
The hound gains 2 feet on the hare with every leap, so it takes 150 ÷ 2 = 75 leaps to close the gap. In those 75 leaps the hound covers 75 × 9 = 675 feet (the hare covers 75 × 7 = 525 feet — exactly 150 feet less). It's one of the 'Propositiones ad Acuendos Juvenes' ('Problems to Sharpen the Young'), roughly 53 riddles attributed to Alcuin of York, the English scholar who ran Charlemagne's court school around 800 CE — one of the oldest surviving collections of recreational math in the Western tradition.
— Alcuin of York (attributed), Propositiones ad Acuendos Juvenes — c. 800 CE