News from Mathnasium of Hinsdale

2021 in Roman Numerals is MMXXI

You may see Roman Numerals on some older clocks, or on the outside of old buildings. Instead of using place value, each symbol is a set value.  Factmonster (click!) has a brief guide on how to write in Roman numerals. Here's the gist: 1 = I , 5 = V , 10 = X. Letters combined together are added to reach the total value, but each letter can only be repeated three times max. 

If each letter can only appear three times in a row, how can we make 4? We have to subtract! by writing the symbol for one in front of the symbol for five. 4 = IV , 9 = IX .

In the Roman times, four was also likely to be written as four lines: IIII. Find a clock face with Roman numerals. How is the 4 written?

Try it out!

Can you write your age in Roman numerals? What about the year you were born? Check your answer with this conversion tool.

To keep track of bigger numbers, more symbols are introduced. 50 = L , 100 = C . What do you think the M in MMXXI represents?

Are you more into puzzles? Check out Matchstick Puzzles for some visual tricks using Roman numerals. (You don't need matchsticks - you can use pencils, popsicle sticks, or just draw it out!)

Do as the Romans Do

Roman Numerals were used regularly until the 15th century, when Arabic numerals began growing in popularity. (Arabic numerals are what we use today - 0, 1, 2, 3, 4, 5, 6, 7, 8, 9.) The Romans needed their numbers to have practical uses - they needed measurements for roads and buildings, amounts of money, and more. They even used various fractions! Read more about Roman fractions here.

Further Reading

Dr. Math

Wikipedia