Close

How to Read Roman Numerals – The Subtractive Principle

The ‘Subtractive Principle’ in Roman Numerals

how to read roman numbers

How to Read Roman Numbers – The Subtractive Principle

Yep!!! another ‘techo’ word. This time it means to represent some numbers in roman numerals 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.

Hint: When smaller numerals are on the left of larger ones… subtract.

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.

Notable Roman Numeral Quote

‘Class, please! If you don’t learn roman numerals, you’ll never know the date certain motion pictures were copyrighted.’ Edna Krabappel (from The Simpsons)

Take me to the Roman Numbers Homepage

roman numerals lessons

roman numerals home

next roman numerals lesson