"Quotient" is the content of the seventh book of mathematics in nine-year compulsory education, and it is a new lesson. Quotient Invariant Law is a new mathematical law. Dividend and divisor must be expanded (or reduced) by the same multiple at the same time, so the quotient can remain the same. This is a functional idea that students have never been exposed to before. This rule is not only the basis of simple operation of divisor and division with zero at the end of divisor, but also the basis of learning division in primary schools in the future, and it is also helpful to understand the basic properties of fractions. Students have mastered the division law that divisor is three digits before learning textbooks, which provides knowledge and ideological preparation for the study of this topic. Through the teaching of this course, students are required to understand and master the quotient invariance, and use the quotient invariance to perform simple operations on oral division. Students experience success in the process of participating in learning activities such as observation, comparison, conjecture, generalization and verification, and at the same time penetrate the initial enlightenment education of dialectical materialism. According to the above teaching contents and teaching objectives, the teaching focus of this course is to guide students to discover and master the invariable nature of quotient, and the understanding of the invariable nature of quotient is the difficulty of this course. Second, according to students' age characteristics, teaching ideas create effective problem situations, guide students to observe and compare the internal relations of related formulas independently, and explore, discover, verify and apply laws, which not only enables students to master the invariance of quotient, but also enables them to actively participate in the formation of knowledge and cultivate their learning ability. Third, talk about the first step in the teaching process: stimulate interest, question and ask questions. In this step, I arranged two steps, namely arousing interest, asking questions and asking questions. I started with the advertisement of "Fox Brothers Baked Sesame": Little white rabbits love baked sesame seeds. On this day, he came to the "Fox Biscuit Company" in the forest and wanted to buy delicious and cheap biscuits. But the Fox Brothers advertisement stumped it, and I didn't know which one to buy. Brother Fox's advertisement: "240 yuan can buy 40!" Fox's advertisement: "480 yuan can buy 80!" Fox three brothers' advertisement: "4800 yuan can be wholesale 800!" " "Fox Brothers' advertisement:" 60 yuan can buy 10! "Fox Five Brothers' advertisement:" 24 yuan can buy 4 baked wheat cakes! "Through the calculation of these five formulas, the students found that the unit price of baked wheat cake is 6 yuan. At this time, Brother Fox posted an advertisement: "Each baked cake: (24÷ 13)÷(4÷ 13)= () yuan", which triggered a cognitive conflict among students about "doubt" and made them want to stop. When their learning behavior encounters obstacles, let them observe the front. "Under what circumstances will the business remain unchanged?" Mathematical problems, such as clear learning goals, play a goal-oriented role. Part II: Analyze the problems and summarize the laws. In this part, I have arranged three steps: first, let students discover the law independently, then verify the law, and finally deepen their understanding of the law. First, guide students to observe the first five formulas in the story situation, and observe the "change" of dividend and divisor in other formulas with "240÷40=6" as the standard. And write them on the blackboard: 240 ÷ 40 = 6 480 ÷ 80 = (240× 2) ÷ (40× 2) = 6 4800 ÷ 800 = (240× 20) ÷ (40× 20) = 6 60. Invariance, and then let the students discuss in groups. A group of students explore the situation that dividend and divisor are expanded by the same multiple at the same time. Two groups of students study the case that the dividend and divisor are reduced by the same multiple at the same time, and then collectively summarize the "quotient invariance" and emphasize "simultaneity" and "division by 0" to improve the concept. Of course, the conjecture put forward by incomplete induction is not completely reliable, and for primary school students, the hypothesis put forward can only be tested by another example. Therefore, I ask students to write examples to verify, so as to cultivate students' scientific thinking methods. Finally, I aim at students' mistakes and omissions, and let students deeply understand the law through real-time exercises such as "judging a sentence" and "filling a sentence". 350 ÷ 50 = (350 ÷10) ÷ (50 ÷10) 75 ÷ 25 = (75× 4) ÷ (25× 4) 360 ÷. 200 ÷ 40 = (200× 4) ÷ (400×) = (200×) ÷ (40 ÷ 5) = (200× 7) ÷ (○) Which page is it? Find it yourself!