First, the thinking of oral calculation should be in step with that of oral calculation.
Oral arithmetic is "mental arithmetic", which is a calculation method based on thinking and language to get results. Oral calculation plays an important role in the whole calculation teaching and is the basis of estimation and simple calculation. To improve students' computing ability, we must lay a good foundation for oral calculation. However, in the classroom reform, some teachers ask students not to use the idea of verbal calculation, but to use the idea of "verbal calculation by writing", which is just that students apply the idea of verbal calculation to verbal calculation. Imagine, when the number is very large, can students do this orally? However, the real idea of oral calculation and the concept of oral calculation pass by here, which shows that the idea of oral calculation and the concept of oral calculation are out of step, and attaching importance to oral calculation has become a complete empty talk. This will inevitably lead to the acquired bad development of students' oral arithmetic ability, which will cause immeasurable losses to students' follow-up study. Therefore, in computing teaching, we should strengthen the training synchronized with oral calculation methods, pay attention to students' understanding and implementation of basic algorithms when doing oral calculation, pay attention to the internalization of students' oral calculation ideas, help students learn to flexibly choose oral calculation methods according to actual conditions, let students understand and master the real oral calculation methods, feel the value of oral calculation in oral calculation, and arouse students' demand for correct oral calculation.
Second, in the process of calculation teaching, we should pay attention to the harmony and unity of oral calculation, written calculation and estimation.
Oral calculation, written calculation and estimation are all important contents of mathematical calculation in primary schools. Mathematics curriculum standards also clearly put forward "strengthening oral calculation and attaching importance to estimation", "being able to estimate the operation results and explain the rationality of the results", "being able to estimate in combination with specific situations and explain the estimation process" and "being able to choose appropriate estimation methods and develop the habit of estimation in the process of solving specific problems", which all reflect the importance attached by curriculum standards to estimation teaching. In the teaching process, we should pay attention to cultivating students' estimation consciousness, optimizing students' estimation strategies and improving students' estimation ability. Estimation is closely related to oral calculation and written calculation. Oral and written calculations can often provide sufficient "material" for estimation, and then promote the proficiency of oral and written calculations. Estimation can be regarded as an important calculation strategy. It is not only a necessary tool to solve practical problems, but also an important basis for accurate calculation. In practical teaching, they cannot exist in isolation. Therefore, in the calculation practice, it is necessary to strengthen oral calculation and implement written calculation, so that students can master all kinds of estimation skills skillfully, form estimation skills, develop the habit of verifying fine written calculation with estimation, and improve their calculation ability.
Third, actively create a suitable teaching situation
1. The situation created should be closely combined with students' existing life.
It is necessary to create certain situations in computing teaching. The new curriculum standard clearly points out that students should learn mathematics in life, feel the close relationship between mathematics and life, and solve practical problems in life with mathematical knowledge. However, the situation created must conform to the age characteristics of students and be close to their lives, so as to arouse students' interest in mathematics. Let students feel new knowledge independently in the learning situation. This design makes the calculation class get rid of "boring" and increase "lively and interesting", closely combines the teaching situation with the teaching content, organically combines reviewing old knowledge with introducing new courses, and lays a good foundation for developing new courses.
For example, in the multiplication of seven, the teacher suggested that each ladybug has seven black spots on its shell. Where did you find "seven" in your life? After discussion, the students come to the conclusion that there are seven colors, tangram, seven days a week and so on. After learning the multiplication formula of 7, the teacher used a short story to guide the students to remember: the Monkey King stayed in the blast furnace for "7,749 days", ... regardless of "7,721", it was closely combined with students' life, which was both interesting and practical, and enhanced students' interest in learning.
2. The situation created should be convenient for students to explore and understand the calculation.
Creating situations can not only be vivid and novel on the surface, but also stick to too much non-mathematical information, and can not interfere with and weaken the learning of mathematical knowledge and skills and the development of mathematical thinking. Situation creation is a means, not an end. When creating situations, it is convenient for students to explore calculation methods and understand reasoning. For example, when the "carry addition" in the first semester of senior one is 9+5=, you can create a situation in which a little monkey buys peaches. The box has 10 cubes, with 9 peaches inside and 5 peaches outside. How many are there? This situation is convenient for students to explore the calculation method through operation. The ten squares in the box can easily remind students of the method of ten plus four. If the box with lattice in this case is replaced by a basket, the effect will be very different. It is important to create situations to serve computing teaching, and never create for the sake of creation.
3. The creation of the theme map is close to the reality of students' life.
The creation of thematic maps is the same as the creation of scenes, which brings vitality to computing teaching in the new curriculum reform. It has changed the tedium of traditional computing teaching and made computing teaching closely linked with real life. However, the richness of thematic maps also requires our teachers to think rationally and guide reasonably, otherwise it will lose its practical significance. Computing teaching needs to create a scene according to the topic map, and more importantly, it is necessary to use the topic map in the textbook reasonably. The purpose of scenario creation in computing teaching is to extract mathematical materials from life and let students experience the relationship between mathematics and life. To solve problems, students should be guided to analyze the relationship between the provided mathematical information and the questions they want, and to explore methods and strategies to solve problems. Once they deviate from this center, computing teaching will lose its direction.
Fourth, pay attention to students' learning starting point and improve the basis of the effectiveness of computing teaching.
Ausubel, an American educational psychologist, once said: "The most important reason that affects learning is what students already know, so we should teach according to students' original knowledge. "... teachers should pay close attention to students' learning starting point and carry out targeted teaching activities accordingly. However, in actual teaching, some teachers only design and carry out teaching activities from their own "subjective wishes" such as mastering teaching materials and understanding knowledge, ignoring the starting point of students' learning, treating students as a "blank sheet of paper" and carrying out teaching activities step by step according to the preset teaching plan before class, thus making classroom teaching exist in name only. For example, in the teaching process of "multiplication formula of 6", some teachers ignore that some students may have been able to recite "multiplication formula of 6" skillfully, so that when students propose to use multiplication formula, the teacher will say "multiplication formula has not been learned"; Or when some students skillfully recite "multiplication formula of 6", they don't know where to start in the later teaching, or ignore the students' learning experience and blindly follow their own plans, which will inevitably affect the teaching effect. Teachers should fully grasp the realistic starting point of students' learning, organize teaching from students' point of view, adjust teaching procedures flexibly and tactfully according to students' reality, pay attention to classroom generation and students' emotional experience in class, and make our computing teaching full and effective.
Fifth, handle the relationship between algorithm diversification and optimization.
Algorithm diversification embodies a brand-new teaching concept, which is an effective way to teach students in accordance with their aptitude, promote their all-round development and cultivate their innovative spirit. By making students try to diversify their algorithms, they not only broaden their thinking, but also provide them with opportunities to communicate and learn from each other. While experiencing the diversity of algorithms, you can change yourself and enhance your understanding. However, it is not conducive to the formation of students' computing skills if they blindly emphasize the diversity of algorithms, excessively seek novelty and diversity, and excessively respect students' personalized but not necessarily simple algorithms in the teaching process. Only on the basis of the diversity of algorithms, further guide students to compare and summarize, and optimize the algorithms appropriately, can a more efficient calculation method be formed. For example, in the teaching of "two-digit addition and subtraction (no carry)", when students are asked to discuss how to calculate "43+3 1", they come up with the following algorithms: algorithm 1: to calculate with a counter, first dial 43 on the counter, then dial 1 on one digit and 3 on the tenth digit to get 74; Algorithm 2: 40+30 is 70, 3+ 1 is 4, and 70+4 is 74; Algorithm 3: 43+30 is 73, 73+ 1 is 74; Algorithm 4: 43+ 1 is 44, 44+30 is 74; Algorithm 5: first align the unit with the tenth place, then 3+ 1 on the unit is 4, and 4+3 on the tenth place is 7, which is 74, and so on. Teachers should not be busy evaluating, first affirm students' ideas, and then ask: which method do you think is simpler and more useful? Further guide them to analyze the characteristics and advantages of various algorithms, so as to realize the self-optimization of the algorithms. Computing teaching should not only reflect the diversity of algorithms, but also optimize them. However, the process of optimization should be given to students, so that they can experience the further optimization and screening of query results, cultivate their awareness and ability of optimization and screening, and improve their mastery and understanding of knowledge.
6. Designing diversified training is an important way to improve the teaching effect of computing.
Practice is an important part of computer teaching, which consolidates what students have learned, is an important way to form skills, skills and improve the effect of computer teaching, can cultivate students' thinking ability and creativity, and is also a powerful measure to test students' mastery of new knowledge. Teachers should design diversified exercises according to the content characteristics of computing teaching and the actual situation of students, so as to stimulate students' interest in learning, so that students can know the results of their own exercises in time, find mistakes in time, correct them and improve the teaching effect. In particular, it is very important for students to design some targeted exercises that are easy to make mistakes in the calculation process, so as to correctly master the calculation methods and table skills.
Seven, pay attention to cultivate students' good computing habits.
Good computing habits are a reliable guarantee for students to calculate correctly, which directly affects the formation and improvement of students' computing ability, so it is particularly important to cultivate students' good computing habits. The first is to cultivate students' habit of carefully examining questions. When calculating, students are required to observe numbers and symbols carefully to see what their characteristics are and what their internal relations are. Then make clear their operation order, make clear what to calculate first, then what to calculate, and then compare, choose and determine the appropriate calculation method. Finally, I began to calculate. The second is to cultivate students' good writing habits. Students are required to be standardized in calculation format, neat in writing, calm in thinking and patient in calculation. The third is to develop the habit of self-examination. Teachers should teach students how to check and calculate, ask students to check their own calculation process and results after calculation, and gradually develop the good habit of consciously checking, checking and correcting errors.
In short, we should start from the characteristics of computing teaching, the reality of students, and the psychological characteristics of children, so as to create a learning environment full of childlike interest and vitality for lower-grade children, so that students can enjoy and love learning, so that boring computing teaching can glow with new vitality, and the computing classroom can make students full of expectations!
Make auxiliary lines as shown in the figure.
Zheng DF parallel AC
Angle BFD = ¡Ï FDB = 36 = ¡Ï Ade
Certificate EF=ED=DB?