About “Jigu Suanjing”
Jigu Suanjing was written by Wang Xiaotong, an early Tang dynasty calendarist and mathematician. It was completed before 626, the year he presented it to the Emperor. The text was required reading for the Imperial examination. Studying Jigu Suanjing took three years, the same amount of time required for studying The Nine Chapters on the Mathematical Art and Haidao Suanjing. (Summary adapted from Wikipedia, CC BY-SA 4.0.)
Some summaries adapted from Wikipedia, CC BY-SA 4.0.