Sexagesimal numeration is a numeral system in which all derived units are based on the number 60 and the powers of 60. The word sexagesimal is derived from the Latin word sexagesimus (sixty). Between 4000-3000 b.c. the Sumerians developed a sexagesimal number system that had an additive decimal (base-10) sequence of "1 to 10, 10 to 60, 60 to 600, 600 to 3600, and so forth". For example, the Sumerian number of 100 was expressed as "1, 40"; that is, one unit of 60 plus 40. The year 2000 would be expressed in this system as three units of 600, plus three units of 60, plus 10 plus 10. Ptolemy and other Alexandrian astronomers also used sexagesimal fractions that are believed to have been one way that led to the persistent use of the base 60 for measures of time and angles. This is in spite of the nearly worldwide adoption of base-10 numeration for most other measurement needs (currency, the metric system, etc.). For instance...