Do you know that the letters C, D, I, L, M, V and X are Roman numerals that were used by the ancient Romans and still used today? Help Eric to discover the Roman numerals. It's not magic ... it's mathematical! The Pedagogical Side: This segment explores a different way of communicating numbers by using numbers 5 and 10 as landmarks and the Romans method of counting using letters of the alphabet. Roman numerals were used throughout Europe until the Middle Ages and they are still used in the names of the monarchy, dates of film production, buildings and clocks.