system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:How did ancient Romans do complicated math using Roman numerals?
gpt
The normal method of calculation in ancient Rome, as in Greece, was by moving counters on a smooth table. Originally pebbles (calculi) were used.  Marked lines indicated units, fives, tens etc. as in the Roman numeral system. This system of 'counter casting' continued into the late Roman empire and in medieval Europe, and persisted in limited use into the nineteenth century.