How did the Romans do arithmetic with their numerals?

What is CCXXIV x LXXVIII? It wouldn’t have been much fun learning maths in ancient Rome.

9th June 2018
How did the Romans do arithmetic with their numerals? © Getty

Asked by: Kathleen Hughes, New York, USA

Despite our extensive knowledge of the Romans and their works, little is known about how they performed even basic arithmetic using their notoriously unwieldy numerals, where a two-digit number like 78 becomes the seven-letter horror LXXVIII.

But research by cognitive scientists has shown that despite appearances, calculations with Roman numerals can be broken down into steps needing relatively few intermediate results to be remembered. With practice and the use of an abacus, such rules might explain how the Romans coped with the sums needed to build and maintain an empire.

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