How to Read Roman Numerals – The Subtractive Principle
The ‘Subtractive Principle’ in Roman Numerals
Reading Roman Numerals
The technical term ‘subtractive principle’ simply means when smaller numerals are on the left of larger ones you subtract them to get the total.
IV = 1 before 5 = 4
IX = 1 before 10 = 9
XL = 10 before 50 = 40
XC = 10 before 100 = 90
CD = 100 before 500 = 400
CM = 100 before 1000 = 900
Personally I like the way it is shown on the graphic but you’ll have to work out which way works for you.
Take me to the Roman Numerals Lessons