Xiao Jiujiu, also called Jiujiu multiplication table, is a multiplication formula for beginners when people study mathematics. Contains the multiplication formula from 1 to 9, 36 sentences. The inventor and perfecter of Xiao Jiujiu was Jiu Shao, a mathematician in the Spring and Autumn Period and the Warring States Period. Xiao Jiujiu is not only used in multiplication, but also widely used in other mathematical problems. 999 is also a kind of multiplication formula, the full name is 999 vertical multiplication, which is widely used in multiplication operation. Jiujiu includes 9*9 multiplication formula and 8 1 sentence Jiujiu multiplication vertical formula. Compared with Xiao Jiujiu, the calculation is simpler, but the scope of application is wider.