The ‘Subtractive Principle’ in 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.
e.g. XL = 50 – 10 = 40
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 Numbers Homepage