CASTING OUT NINES
few historians agree on the origin of the process of "casting out nines." Its discovery has been credited to sources as diverse geographically as Arabia, India, and Rome, with dates ranging from the third to the twelfth century. A Roman, Hippolytos, is one of the first known to have used this process. He employed the excess of nines during the third century in connection with gematria.
Casting out nines was used in Arabian arithmetic, beginning with that of al-khowarizmi in the ninth century, to check computation. However, Mach Arabian mathematic is know to have come from Greek and Indian sources, and some historians credit the Hindus With discovery of the process. Hindu astronomers definitely usrd it through the twelfth century.
The casting-out-nine process passed to the west from the Arabs. It appeared in the works of the Italian Fibonacci (1202), the German Widmann(1489) and the Englishman Recode (1540), and if was brought to America by Isaac Greenwood(1729). It disappeared from American textbooks during the nineteenth century, but is was restored after 1900.