The Compendious Book on Calculation by Completion and Balancing

The Compendious Book on Calculation by Completion and Balancing (, "al-Kitāb al-Mukhtaṣar fī Ḥisāb al-Jabr wal-Muqābalah"; ), also known as Al-Jabr (), is a mathematical book on algebra written by Muḥammad ibn Mūsā al-Khwārizmī around 820 CE. "Al-Jabr" was important in the history of mathematics, the term "algebra" itself derived from "Al-Jabr".
Area and volume.
The book show ways of finding area and volume. These include approximations of pi (π), as 3 1/7, √10, and 62832/20000. This latter approximation, this equals 3.1416, which appeared in "Āryabhaṭīya" (499 CE).