PCO stands for Potential Change Order (construction management). Suggest new definition. This definition appears somewhat frequently and is found in the following Acronym Finder categories: 1  Business, finance, etc.
Quick Answer. The Roman numeral XIX is the number 19. X is the number 10, and I is the number one. When a lower number is placed in front of a larger number, it indicates subtraction; IX is the same as 10 minus one, which equals nine. The Ancient Romans used different letters to represent numbers.
Place value. Roman numerals can be changed into Hindu-Arabic numbers by taking the place value columns (highest lowest) of the Hindu-Arabic number and gradually building up the Roman numeral. Example: The Roman numeral for 2 305 is MMCCCV. Example: 99 = 90 + 9. or XC + IX XCIX. So, XCIX is the Roman numeral for 99.