First of all, from the perspective of using textbooks, this is a good lesson:

1. Simplify the teaching process by introducing what students are interested in, and let students get to the point. On the basis of students' existing knowledge, experience the meaning and function of using letters to represent numbers, and understand and master the method of using letters to represent numbers.

2. Let's learn to use letters to represent numbers, and we can use formulas containing letters to represent simple quantitative relations.

3. Let students experience the abstract process of expressing practical problems with formulas containing letters, establish a preliminary sense of symbols and algebra, appreciate the value of mathematics, establish and cultivate a preliminary sense of exploration and creation, and develop the ability of abstract generalization.

Second, the shortcomings:

There is no concept of osmotic function.

Third, in daily teaching, I understand and grasp the teaching materials like this:

When I was studying estimation in the second grade, I designed such a math activity in class. I wrote eight addition and subtraction problems (written on a small piece of paper): 59+1148+2217+29 82-6196-178-30. In the headquarters, some students are calculating by hand and some are estimating. As a result, the students who use estimation are the fastest. I asked them to talk about the estimation method and why they thought of it. Finally, we come to the conclusion that "estimation" can be used when the calculation is not so accurate, which is more convenient for calculation. Then let students know the methods and uses of estimation in solving practical problems (solving practical problems of examples). Estimation of students' first contact. In order for students to learn, we must first understand why they want to learn and what is the use of learning, so that students will have the purpose, interest and motivation to learn it well. Mathematics comes from life and is also used in life. Only when estimation is used to solve practical problems can we truly realize the function of estimation and master its methods. It is much more flexible and easier to stimulate students' appetite through this kind of premise activity than to solve the practical problems of examples rigidly according to books. Therefore, we should not only make good use of teaching materials, but also "use them flexibly". Establish a correct view of teaching materials, on the basis of careful analysis of the curriculum objectives to be achieved by teaching materials, closely contact the social practice and students' life experience at that time, select specific teaching materials, and make necessary adjustments to the teaching content, such as adding, replacing or reorganizing. Courses in the new period are both "text courses" and "experience courses", which fully mobilize students' enthusiasm and initiative, thus completing teaching tasks.