Roman numeration system

The Roman numeration system evolved around 500 BCE. Just like other anscient numeration systems, it uses special symbols to represent numbers.

The basic Roman numerals are the followings. Study them and memorise them if you can. It could become handy one day

Any other roman numerals are found by combining these basic numerals


1) 154 is equivalent to CLIIII in Roman numerals

2) 1492 is equivalent to MCCCCLXXXXII in Roman numerals

3) 3495 is equivalent to MMMCCCCLXXXXV in Roman numerals

Over time, two useful attributes were introduced that made the Roman numeration system very useful and efficient

The first one is the subractive principle

With the subtractive principle, Roman numerals can be combined or paired so that when reading from left to right, the values of the symbols in any pair increase.

The value of the new pair is:

bigger number in the pair − smaller number in the pair

For instance, I can pair I and V to make IV and the value of this pair will be V − I = 5 − 1 = 4

I can pair C and D to make CD and the value of this pair will be D − C = 500 − 100 = 400

I can pair X and L to make XL and the value of this pair will L − X = 50 − 10 = 40

four thousand and ninty thousand in roman numerals

This subtractive principle will make the writing of examples 1), 2), and 3) a lot simpler



Instead of CCCC, we can pair C and D to get CD and CD = 400 as demonstrated above

Also, instead of LXXXX, we can pair X and C to make XC since XC still equal to 90

Replacing CCCC (in bold) by CD, we get:


Replacing LXXXX by XC (in blue), we get:


So, instead of using 11 symbols, we can just use 7 to represent the same number


The second one is the multiplicative principle

Basically, a horizontal bar above any number means 1000 times the number


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