Classification and sorting require students to classify according to given standards, master the methods of classification and counting, understand the consistency of classification results under a single standard, learn to classify according to different standards, experience the diversity of classification results under different standards, customize classification standards according to specific conditions, and understand the practical significance of classification.

"Number and Algebra" is an important part of compulsory education mathematics curriculum. This part includes the concept of number, the operation of number and the estimation of quantity. Letters represent numbers, algebraic expressions and their operations; Equations, equations, inequalities, functions, etc. The teaching course content that does not belong to the first grade.