The knowledge system of primary school mathematics mainly includes four parts: number and algebra, space and graphics, statistics and probability, practice and comprehensive application.

Number and Algebra is divided into five parts: number understanding, number operation, common quantities, equations and exploring laws.

"Understanding of numbers" runs through all grades of primary schools, mainly involving the understanding of natural numbers, decimals and fractions.

The second volume of Grade Three requires students to express large numbers in trillions. For example, China has a land area of 9.6 million and a population of 654.38+04 billion, and it can be estimated that the number is larger. The estimation study here requires students to know how to estimate, know the equal sign, and learn to write and read the estimation.