How to read and write roman numerals?

In Latin, numerals were written using letters of the alphabet. These Roman numerals are still used, in addition to our more common numerals based on the Arabic system. The basic principle of Roman numerals is that when a smaller number precedes a larger one, it is subtracted from it. When it follows, it is added.

The first 10 Roman numerals are I, II, III, IV, V, VI, VII, VIII, IX, X. In these you can see the basic principle at work: four is IV, while six is VI. In the first, the one is subtracted from five because it precedes; in the second, it is added because it follows.

A letter repeated repeats Its value. For example, XX is 20 (10 plus 10), and XXX is 30 ( 10 plus 10 plus 10). Other numerals are L for 50, C for 100, D for 500, and M for 1,000; 40 is XL; 60, 70, and 80 are LX, LXX, and LXXX; and 90 is XC. A line over the top of a numeral multiplies its value by 1,000.