c. 980-1037

Arab mathematician who wrote an important work on arithmetic and number theory. Raised in Baghdad, al-Baghdadi moved to Nishapur in what is now Iran; eventually, however, political turmoil forced him to flee to the smaller town of Asfirayin. There al-Baghdadi, who came from a wealthy family, taught for free in the local mosque. Though he wrote primarily on theology, he produced two mathematical works, the more significant of which was al-Takmila fi'lhisab. In this work, he examined differing arithmetic systems, including counting on the fingers, the sexagesimal system, and Hindu numerals, which he favored. The work also addressed the subjects of irrational numbers and business arithmetic.