Example 1 is a scene where students watch a puppet show, which leads to math problems. This arrangement of teaching materials is to let students understand information and find problems by observing the situation map. The key point is to learn to solve problems with comprehensive formulas. The information here has explicit information, such as "there were 22 people who saw the play", and some invisible information, such as how many people left and how many people came. Therefore, in teaching, teachers must clearly put forward the requirements and problems to be solved after students fully express their opinions, and guide students to observe problems from different angles, so as to adopt different methods to solve problems. In class, we can explore independently or study in groups. Either way, students should be organized to exchange their views and ideas in groups on the basis of independent thinking. After full discussion, the whole class will share different ideas to solve the problem.

Student's calculation method:

1, 22+ 13=35 (person) 35-6=29 (person)

2,22-6 =16 (person) 16+ 13=29 (person)

3,22+13-6 = 29 (person)

4,22-6+13 = 29 (person)

Students may be able to list these methods, but they may not think that teachers should organize students to sort out the internal relations between different ideas and different algorithms. It should be emphasized that this kind of problem can also be calculated by comprehensive formula.

Example 2 is the case of a bakery. The key to solving the problem is to learn to use parentheses to synthesize formulas and understand the function of parentheses. Solve the practical problem of "how much is left" through the familiar situation of buying bread. It can still guide students to think from different angles. One way of thinking is to formulate them step by step: 54-8-22 or 54-(8+22). One way of thinking is to list comprehensive formulas. In the textbook, it is particularly emphasized that "brackets should be used when writing formulas", which is the focus of teaching, so it is necessary to make clear why "brackets should be counted first when calculating". Because it is the first time to use brackets in a presentation, if students have questions, teachers can organize students to review old knowledge and make use of real situations to clarify the necessity and usage of brackets.

When teaching Example 2, a teaching method similar to Example 1 can be adopted. First, let the students look at the pictures on the next page, ask questions and inspire them to think about how to solve these problems. Let the students fully discuss and talk about their own ideas, and then focus on the way to solve the problem. When calculating the formula, we can formulate it step by step, and emphasize the internal relationship between the two formulas. When synthesizing formulas, we should emphasize the purpose of using parentheses.