1. Test students' proficiency in multiplication formula, because multiplication formula is a tool for multi-digit multiplication and multi-digit division.
2. It is to cultivate the analytical ability of applied problems (a, understanding of mathematical terms in the problem. B, find out the relationship between the sentences in the question. C, if you can use line segment analysis, use line segment analysis to represent the quantitative relationship diagram in the question, and establish the formula of addition, subtraction, multiplication and division.
3. It is the memory and exchange of area units.