How to guide students to understand the essence of mathematical formulas in teaching
First of all, the "some operations" on the right side of the Curriculum Standard has new requirements in mathematics courses, and students should pay attention to the development of computing ability. Computing ability is the ability to carry out the main business according to the correct laws and arithmetic rules. Cultivate students' ability to understand the management of arithmetic operators and seek reasonable methods to solve simple arithmetic problems. In the Interpretation of Curriculum Standards, it is also emphasized that "it is more important to downplay the requirements for computing power and choose accurate calculation results to get the right method than skilled operation. Pay attention to whether students understand the operation. In fact, the result of the operation can be accurately obtained, not just the speed of the operation. " To achieve this goal, teachers are required to master the number of teaching operations, not only focusing on students with arithmetic skills, but also paying attention to the examples that students can understand and master the learning process of algorithms, that is, paying attention to treating teaching and algorithms as an organic and reasonable combination, so as to cultivate students' computing ability. The flow of learning process is the quantitative development of arithmetic and logical thinking ability, and there are internal relations among the existing calculation concepts, properties, rules and formulas, which are strictly logical. The introduction and establishment of every concept, property, law and formula goes through the thinking process of abstraction, generalization, judgment and reasoning. Students learn, understand and master the contents of "some operations", from concrete to abstract, from perceptual to rational, and even from general deduction to concrete treatment and put them into practice. Therefore, arithmetic learning is conducive to the development of students' thinking ability. This requires teachers not only to pay attention to the results in the teaching process, but also to the methods and thinking processes of obtaining the results. It is reasonable to understand the students' thinking process and master the algorithm flow. Students are still thinking about the main visual images, but they think rationality and algorithm are abstract. Therefore, how to deal with the relationship between arithmetic operation and the characteristics of algorithm teaching in students' thinking teaching is a difficult point. We can combine students' age characteristics, interesting fairy tale scenes and intuitive models, and use students' existing knowledge base, life, relationship management and algorithms to deal with the teaching experience of arithmetic operation. Second, (1) teaching refers to dealing with arithmetic operations and the relationship between management and algorithms through interesting fairy tale scenes. Students, especially younger students, think more intuitively, thus creating interesting fairy tale scenes, which not only stimulates their self-motivation to learn well, but also helps them better understand an example in fairy tale scenes and master the help of algorithms. Primary school teachers in Beijing are giving Hong Wei a lesson of "carry adder below 20" to create a fairy tale scene (PPT) for students, a cute little animal. First of all, Wei felt that the teachers helped nine small animals in the car and inspected more than a dozen port operators. The enthusiasm of the students was mobilized at once, because they could use the first stop of what they learned to help small animals be happy. Then through the second stop to help five small animals, the car commented on Canada and asked, "Is there any good way for us to think again quickly?" Let students feel that it is quick to scrape "ten" and count "ten plus several" for the first time, and it is easy to understand the reason why "carry plus" counts. Five hours after the animal car, the total number of small animals on board after nine small animals stood together for the first time? This leads to 9 +5 =? How does the carry adder calculate 9 +5 =? Students soon think that 10 consists of 50% 1 and 4, 1 and 9, 10 plus 4 equals 14. Therefore, students can understand and successfully master the addition theory and algorithm in a relaxed and happy fairy tale situation. Through this lesson, we can see that Mr. Wei can combine his age, students' psychological needs and students' thinking characteristics to create interesting classmates and favorite fairy tale scenes, make boring mathematics interesting, turn abstract operators into intuitive image processing, and let students master natural algorithms and be sensible successfully. (B) intuitive model and reasoning and algorithm teaching, in order to deal with arithmetic operations. Huangchenggen Primary School, Shi Dongxue's "Double Number Multiplying Double Number", the history class of the third grade primary school teachers combines the thinking characteristics of students, and has an intuitive model to better deal with the relationship algorithm between managers and operators. History teachers don't have to write "vertical" as the ultimate teaching goal of this course, but students have been able to master students' vertical guidance, preliminary accounting methods and explore the truth behind the methods. And provide students with an intuitive map of ideas as research materials. In the research, the students put forward various results. Students have different rules, but the idea of "being together after the first minute" is the same. Is this the basic idea? Vertical multiplication operation. After that, the teacher's ideological history is re-divided, and the tall and straight figure of four sentences gives the corresponding formula to guide students to calculate the longitudinal depth of the truth behind each detail step by step. The idea of "graph" is not only the accumulation of activities, but also creates valuable experience opportunities for students, and also helps students to better understand the truth behind the two-digit multiplication algorithm. In our previous teaching, many teachers did not attach importance to or guide students to explore calculation, or just explored methods. Students' learning guides students to stand upright immediately, standing upright in all aspects of students, without really understanding the operation process and pursuing calculation methods. This may lead to students not really understanding that case law depends on the acquisition methods and skills of memory. This is obviously not conducive to the development of students, and the history teacher is precisely the course students through the process of understanding, truly and solidly provided a vivid typical case. In teaching, teachers should be willing to spend time to give students an opportunity to experience, understand, understand and create. The new curriculum standard also clearly points out that the experience of student activities and the profound goals behind it need teachers to dig their brains and concentrate on understanding in practice. (c) Using students' existing knowledge and life experience, relationship management and algorithms to deal with the basis of arithmetic calculation teaching. Ping An, a primary school teacher in Beijing, has been doing "decimal addition and subtraction". In this class, the teacher has a lesson to help students master the knowledge base and life experience, and to help students understand the basic principles of decimal addition and subtraction operators. The teacher asked the students to call the roll in the independent series, which has sorted out a student's score of 0.8 +3.74 = this type will reveal "decimal point alignment", which is an important summary when the focus of this lesson is on decimal subtraction algorithm. In order to give students a chance to experience the existing abstract thinking processes of integer addition and subtraction, empirical judgment, reasoning and cognitive mobilization, teachers let students try to do each one by themselves and explain why they do so. Teacher: You have done a lot of addition and subtraction problems, all of which are aimed at the bottom two numbers without exception. Can you make this question entitled What not to do at the bottom? Health: The last one is a bit integer, which is a bit bottom-aligned. Decimals are not necessarily the same last digit, which is not bottom alignment. Teacher: Even if you don't have an aligned bottom, who does? Health: decimal point alignment, that is, the same number corresponds. Teacher: You see deeply and accurately. There must be a reason for this. Why do decimal points have to be aligned with the same number? Health 1: If you misplace it, the calculation is wrong. Health 2: If you don't align the decimal point, but align it with the bottom, and then divide one eighth by four percent to align it, and then add it up, it will definitely be incorrect. S3: Well, for example, I bought two things, one is 0.8 yuan and the other is 3.74 yuan. If the last digit of the sum of 8 and 4 is 8 plus 4 points, it is definitely wrong. Teacher: We studied the same problem. We can study it from different angles. For example, you can tell the truth, and so can you, such as children. On this issue, some students think that we are all familiar with explaining simple things. The example of "money" illustrates a profound truth. You're great. There seems to be only one thing that can count the addition and subtraction units. Summary: It seems to be different from integer addition and subtraction. In fact, "decimal alignment" and "bottom alignment" are the same, and the reason behind the alignment of the same number of digits is "direct subtraction of the same number of crimes". It's great that you not only found the method, but also understood the mathematics behind it. What occupies the position of decimal addition and subtraction in primary schools? Learning field of "number and algebra"? How to grasp its relationship with integer addition and subtraction? In this lesson, how to show the essence of knowledge and grasp the core concepts of teaching? The teacher's teaching practice is to answer the above questions. In the process of guiding students to explore decimal addition and subtraction methods, teachers have always grasped the "soul" of implementing teaching knowledge courses. She is not satisfied with the students' correct calculation results, but guides them to understand the essence of mathematics step by step. Enlighten students to deeply understand the meaning of decimal number addition and subtraction, that is, decimal integer addition and subtraction are consistent in nature and meaning, that is, addition and subtraction with the same number. Therefore, the organic combination of "unreasonable" and "explicit method" is helpful for students to understand the basic principles, and the summary calculation algorithm is helpful for students to understand the core concepts of mathematics more deeply, which can better realize the correct calculation operation of "students and legal ability according to law". "the goal. Third, the teaching suggestion of "some operations" (1) deals with the abstract relationship of intuitive operation management algorithms. The reason is not easy to understand. In real life, intuitive maps, such as students' existing knowledge base of students and teachers, help students understand. (2) The relationship between the diversity of processing and algorithm optimization. The algorithm is diversified and pays attention to students' personality. Students can make them prefer another method in this way, but the reasons behind it are the same. The teacher found that students can learn math more effectively by making them understand in different ways. (3) Relationship handling and thinking ability training. This is not a simple, mechanical problem accumulation. In this process, we should focus on helping students gain experience and open up new ideas. (4) Calculate the relationship between life and key problems to be solved.