## Roman numerals

The Roman numeral system was used in Ancient Rome. The numbers consist of combinations of letters from the Latin alphabet representing the different values.

## Reading Roman numerals

Roman numerals are based on seven symbols:

I = 1

V = 5

X = 10

L = 50

C = 100

D = 500

M = 1000

These letters can be combined according to the following rules:

If a letter of a lower value is written before a letter of greater value, it has to be subtracted from the letter of greater value.

For example, the Roman numeral IX is the same as 10(X) - 1(I) = 9

If a letter of lower value is written after a letter of greater value, it has to be added to the letter of greater value.

For example, the Roman numeral VII is the same as 5(V) + 1(I) + 1(I) = 7

You can never subtract a symbol of greater value from a symbol of lower value.

Only I, X and C can be written after a letter of greater value:

I can only be written after V and X

X can only be written after L and C

C can only be written D and M

V, L and D cannot be repeated.

A letter can only be written three times in a number.