Gu Yue traveled to Lin'an in the Southern Song Dynasty and found that the level of mathematics at that time was more advanced than imagined, but ordinary people could not calculate complicated accounts. He opened an "arithmetic hall" and taught vendors to use "Pudijin" (the ancient multiplication table) to quickly calculate accounts. After the teahouse owner learned it, he settled accounts twice as fast; the rice store owner learned fractions and has never been cheated by customers again. He also combined "Nine Chapters of Arithmetic" and modern primary school mathematics to compile a book called "Arithmetic for Children" so that children can also get started. Even officials from the Taishi Bureau came to ask him for advice. Gu Yue said: "Mathematics is not a stepping stone to the imperial examination. It is a tool that everyone can use. People who can calculate accounts will live a clearer life."
