First, contact with reality and find problems

1. Show the activities of various interest groups in the school. Model airplane group 18 Art group, 25 Math group

2. Guide thinking and ask questions. What math questions will you ask? Closely connect with students' campus life, create realistic situations, put mathematics problems in life, let students realize that mathematics comes from life and stimulate their enthusiasm for learning. ]

2. Cooperative inquiry and problem solving

1. Do you have any good ideas about how many people are in the math group? The students answered freely, and the teacher concluded: To know the number of people in the math group, you must add a condition related to the math group. Show me all the conditions. If you want to classify these conditions, how do you plan to classify them? Tell me why. Demonstration: there are more people in the math group than in the model group. The number of math group is less than that of model airplane group and art group. There are more people in the math group than in the model airplane group and the art group. If ............................................................................................................ is the condition on the right, the condition of the number of people in the math group is not directly told to us. Before calculating, we must first find out the conditions related to the math group. Today, we will select three situations from these conditions added by everyone and study them together. Choose three situations: the number of math group is less than the total number of model group and art group; The number of people in the math group is more than the total number of people in the model airplane group and the art group. The number of students in the math group is twice that in the model airplane group and the art group. Who will fully describe these three topics?

2. How do students try to solve these problems independently? Please choose a problem you want to solve, in groups of four, and each student will think independently before communicating with his partner.

3. Group cooperation communication report [Pay attention to students' independent exploration and cooperation communication, give students enough time and space, let each student try to answer, then talk in groups and express their ideas. In this process, students not only master the strategy of solving problems, but also cultivate the subjective consciousness and cooperative spirit. Students have gained the joy of success in the "doing mathematics" activity of independent exploration. ]

4. Observe and compare the prompt questions:

(1) What are the similarities and differences between these three questions?

(2) Tell me about these two titles: What is the two-step calculation?

(3) Why is everyone trying to find the number of students in the math group, but the methods of solving problems are different?

(4) Just now, these questions are all about finding the total number of the model airplane group and the art group. Do you want to compare these questions with their total? Display: the number of students in the math group is worse than that in the model airplane group and the art group. There are twice as many people in the math group as in the model airplane group and the art group. Summary after answering: If you compare the number of people in the math group with the total number of people in the two groups, you must first find out their sum. If it's a difference, you have to find a business trip first, and then calculate it now. There are many two-step application problems like this, but no matter how these problems change, we must first find out the conditions related to the problems and then calculate them.

3. Practical application and popularization

1. There are 3 lilies, 5 roses, 8 water lilies and 2 sunflowers more than the total number of lilies and roses. How many sunflowers are there? Students do it independently. Q: If 3+8 =111+2 =13, how can the conditions be changed?

The school holds various competitions every year, such as skipping rope competition.

(1) Tell me how many times you can jump.

(2) provide accommodation for each other. Guess how many times you can jump?

(3) According to the information provided by the teacher, guess how many times the teacher can jump?

As we all know, whoever performs well will be given a red five-star by the teacher. Now several children in Class 3 (6) are arguing about who has the most red stars. Let's help them distinguish, shall we? Clearly said, "I have five stars." Light light blue said, "I have three stars." Liang Liang said, "My stars are four less than Mingming and Lanlan." Xiao Gang said, "My number of stars is three times that of blue." Xiaohong said, "My number of stars is three times that of Mingming and Lanlan." Let's discuss who has the most stars. And explain why.

[Comment: This exercise design has an open, flexible and uncertain life situation. Students can find different solutions and different answers according to the information provided by the topic. The last exercise is the best example. This kind of teaching creates a broad thinking space for students and enhances their motivation to learn mathematics. ]

Sum up the class and get to know the facts: What did you learn today? What is the happiest thing? Any suggestions for teachers? [Comment: While paying attention to students' knowledge and skills, we also pay attention to students' learning emotions, attitudes and confidence to promote students' sustainable development. ]

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