Scientific American presents Math Dude by Quick & Dirty Tips. Scientific American and Quick & Dirty Tips are both Macmillan companies.

Do you think math is fun? I absolutely think that it should be. After all, math problems are really just puzzles. And puzzles are fun, right? I realize that not all math problems are created equally—sometimes you have to use math to get real world work done. And that certainly isn’t always tons of fun. But math should be fun most of the time. The key to this is approaching problems with the right attitude. For example, do you think today’s topic—adding and subtracting Roman numerals—sounds like fun? For many of you, the answer is “No!” And you may be wondering how this could possibly be useful?

While those are fair questions, the truth is that math doesn’t always have to be serious and practical. Even though you may never need to use the math we talk about today, it’s still fun to puzzle out how ancient Romans could have added and subtracted their rather cryptic numerals. No, this isn’t a skill you need to survive in the modern world. But learning to see the many challenges you’ll face in life as puzzles that can be solved is a skill that will help you survive, thrive, and have fun. So, with that in mind, let’s spend today having a bit of fun puzzling out how the Romans managed to do arithmetic.

Recap: What Are Roman Numerals?
Before we begin figuring out how to add and subtract Roman style, let’s recap how the Roman numeral system that we learned about last time works. In this system, the letter “I” represents 1, “V” represents 5, “X” represents 10, “L” represents 50, “C” represents 100, “D” represents 500, and “M” represents 1,000. To write numbers other than these we combine various symbols together. If a symbol that represents a smaller number is written to the right of a symbol representing an equal or larger number, we add the values together. In common usage, symbols are repeated no more than 3 times in a row.

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