Teaching content: Unit 3 P24-P26, Examples 5, 6 and corresponding exercises in the second volume of Grade Four Mathematics of People's Education Press.

Teaching material analysis: The content of this lesson is multiplicative commutative law and multiplicative associative law. Under the guidance of teachers, students can transfer knowledge by using the rules of addition operation they have mastered, give full play to the advantages of network technology, and strengthen information exchange in classroom learning. Students can guess, explore and summarize the multiplicative commutative law and multiplicative associative law, understand their functions, and pave the way for simple calculation in the future.

Analysis of learning situation: students have learned and mastered the operation law of addition before this lesson. In the calculation of solving practical problems, the application of arithmetic can make the calculation simple, create favorable conditions for students to learn the content of this course, transfer knowledge, and help students to explore, understand and use the multiplicative associative law and commutative law independently.

Teaching objectives:

1, so that students can experience and explore the process of multiplicative commutative law and multiplicative associative law, understand and master the laws, and express them in letters.

2. Understand the multiplication and division method, master the establishment conditions of the multiplication and division method, and initially apply the multiplication and division method to solve simple practical problems.

3. Let students learn to use the law of multiplication to make simple calculations. Experience the application value of algorithm, and cultivate students' consciousness and ability to choose calculation methods flexibly.

4. Cultivate students' thinking ability of observation, comparison, analysis, synthesis and induction.

Teaching emphasis: Understand and master the law of multiplication, and use it for simple calculation.

Teaching difficulty: understanding and mastering the meaning of multiplication table.

Teaching methods and learning methods: this course mainly adopts situation creation method and heuristic dialogue method, supplemented by practice method. In order to stimulate students' subjective initiative, let students learn new knowledge in the process of independent exploration and cooperation and exchange, and truly reflect students' subjective status.

Resource preparation: onion college resources (elementary school mathematics micro-course edition)

Teaching process:

First, create problems, causing thinking

Teacher: Boys and girls, today, Dog Egg students are going to take their children to the supermarket to buy sparkling drinks. What will happen to them? Let's go in and have a look with the teacher.

There are two kinds of packaged drinks in the supermarket. Which is more cost-effective? (Independent investigation, exchange and discussion)

Health: There are as many drinks in two packages, both of which are 12 bottles. Comparing 3×4=4×3, we can see that they are equal.

(Design intention: to cultivate students' ability to think and explore actively. )

Teacher: Kid, you are really eye-catching. You can find the answer by multiplication. Now they're on the roller coaster again. How many people are there on the roller coaster? These two children, right?

(1) Let the students observe whether the two formulas of 7×2 and 2×7 are equal.

(2) Tell the meaning of these two formulas.

Teacher: Next, let's continue to discuss the next content, which is about finding the rectangular area. Please think about these two algorithms. What did you find after discussing the above three scenarios?

Health: The numbers on the left and right sides of the three equations are the same.

Blackboard: 3×4=4×3

? 7×2=2×7

? 9×6=6×9

(Design intention: Let students be independent by creating situations. Call the existing knowledge to solve the problem, paving the way for entering the following inquiry part. )

Second, inspire the Lord to explore and obtain the law.

1. Explore the Multiplication Exchange Rate

Teacher: Students, the factors of the three formulas just now are the same. Although the position is reversed, the result is the same. So, is this common in multiplication? Please imitate the format in the onion mathematics micro-lesson, give three examples that conform to the above rules, and upload them to the public screen in the form of reply.

Students begin to try, then report and show examples of students attending classes in Tencent class.

Teacher: Students, are your experimental results valid? Are there any examples that do not conform to this law? Browse the examples given by other students together. Through a large number of examples, it is verified that the position product of two factors remains unchanged as long as they are exchanged equally in multiplication.

Teacher: Can you express the law of this multiplication by letter formula? Who can express this law concisely and accurately in one sentence? (onion micro-lesson video)

There is a blackboard writing (the position product of two factors is constant, which is called multiplication method of substitution in multiplication operation).

Multiplication exchange rate: a× b = b× a.

(Design intent: Encourage students to explore independently and verify the existence of multiplication and method of substitution. The conclusion of information exchange, integration and exploration through the network has gone through the process of knowledge discovery. )

Practice consolidation

(1) Choose the correct answer according to the multiplication exchange rate.

(2) Calculate the following two questions and check them with the multiplying exchange rate.

25×36= 19×7=

2. Explore the combination rate of multiplication

Teacher: We already know that both addition and multiplication have exchange rates, so there is an associative law for addition and an associative law for multiplication. Now Dog Egg and his good friend come to the gift shop to help the boss clean up three kinds of items. Let's see what happens. First of all, we must solve the problem of the number of marbles. Can you use a different calculation method from dog eggs?

Health: You can calculate 2×5 first, and then multiply it by 7.

Teacher: You are so clever, and so is the shopkeeper's algorithm.

Teacher: Students, can you try to tell the meaning of these two multiplication oral tests?

Teacher: After clearing the number of marbles, let's help the dog with the egg white model and the number of bows. (Play micro-lesson video)

Students explore independently, report by name, display the content on the public screen, and the rest of the students raise their hands to communicate.

Induce knowledge points:

Guide the students to sum up the law through the ratio of additive combination and write the letter representation.

(Design intention: Imitate the learning method of learning multiplication and commutative law, give students the initiative to learn, let students explore and verify independently, prove the existence of multiplication and associative law and experience the process of knowledge discovery. )

Consolidate application and solve practical problems;

Teacher: Just now, we have verified that there are commutative laws and associative laws in multiplication. Next, the teacher will test whether we can correctly use the law of multiplication to solve problems.

Deepening exercises:

Try to calculate the following questions with the learned multiplication combination rate.

(25×5)×2 ? 50×(23×2)?

Students finish it on the computer and give feedback.

First, exchange and share, sum up and improve.

What gains do you want to share through the study of this course? (Students speak first and then reply on the public screen)

Teaching reflection:

The design of the whole class closely revolves around and uses the problem scene of onion micro-class, and teachers and students interact positively. Teachers guide students to explore independently and learn actively, so that students have a sense of accomplishment, and then guide students to use previous research methods to carry out research, from help to release, and cultivate students' ability to explore and solve problems and language organization. In application, letting students discover multiplication commutative law and multiplication associative law independently can simplify the calculation of some multiplication problems and guide students to classify multiplication formulas by using this feature. There are still some details to pay attention to in this course, such as timing. How to motivate students to evaluate each other and promote classroom interaction when students can't meet my preset emergency mechanism. It is also a problem that I need to constantly improve and improve in my future teaching.