Roman Numerals - A Math Lesson on the Subtractive Principle - How Do I Work Out Roman Numerals?

Roman Numerals Subtractive Principle
Roman Numerals Basic Facts
The Roman Numerals Homepage
Roman Numerals Lesson


The 'Subtractive Principle' in Roman Numerals

Yep!!! another 'techo' word. This time it just means that to represent some numbers you need to subtract the value of the smaller number from the larger.

e.g. XL = 50 - 10 = 40

Personally I like the way it is shown on the chalk board but you'll have to work out which way works for you.

When you think you've got it, try these:

- IV =
- IX =
- CM =
- XC =
- CD =

Now make up IV questions for your friends to make sure they have mastered this concept.