First, the teaching objectives of the lecture:
The new curriculum standard points out that there is a lot of mathematical information in real life, and mathematics is widely used in the real world. At the same time, it is also pointed out that students' cooperative spirit should be cultivated initially in the learning process, and students' various abilities should be developed through mathematical activities such as observation and comparison. Therefore, in the teaching of this class, by creating the situation of buying books from bookstores, students can feel that mathematics is around.
Second, say textbooks:
"Decimal addition and subtraction" is the content of the first lesson of Unit 3 of Book 9 of Elementary Mathematics published by Jiangsu Education Publishing House. This part of the content is taught on the basis that students have mastered the meaning and nature of integer addition, subtraction and decimal. This part of knowledge is widely used in later life and further study, so mastering this part of knowledge is of great significance for students to study and solve simple problems in life in the future. Therefore; According to the orientation and requirements of this lesson, determine the following three mathematical goals:
1. Knowledge Objective: Understand and learn the calculation method of decimal addition and subtraction, and know the relationship between decimal addition and subtraction and integer addition and subtraction in the calculation method.
2. Ability goal: to cultivate students' ability of transfer, analogy and abstract generalization through independent inquiry.
3. Moral education goal: pay attention to the cultivation of students' study habits in teaching, and let students develop good calculation habits.
Teaching emphasis: Pay attention to the connection between decimal addition and subtraction and integer addition and subtraction.
Teaching difficulties: understanding the principle and calculation rules of "decimal point alignment".
Three. Oral English teaching methods and learning methods
In the teaching process, according to the teaching content, students' age characteristics and their knowledge, various methods are adopted to fully mobilize students' accumulation and initiative in learning. Students analyze and solve their own problems, thus promoting their ability of reflection and self-monitoring. In the process of guiding students to feel arithmetic and algorithms, let them try, let them actively participate in the formation of new knowledge, and promptly mobilize students to speak their own methods boldly, and then let them compare the correctness and simplicity of the methods themselves. In this way, students can understand arithmetic and algorithms in their own way of thinking, both in their hearts and in their mouths. Then, according to the idea of independent inquiry-discussion-induction, students can discover and master new knowledge by using knowledge transfer. In independent inquiry and discussion, let students actively participate in teaching activities, learn to explore by themselves, provide oral, hands-on and brain opportunities, and let students flexibly grasp the teaching key points and break through difficulties in experience, perception, discussion, cooperation and comparison.
Fourth, the teaching procedure:
Investigation and analysis:
Before teaching decimal addition and subtraction, I made a simple survey of several students in my class and found that some students already knew how to add and subtract decimals. How to go to a class where many students know the conclusion?
In terms of teaching arrangement, according to students' cognitive level and knowledge mastery, three teaching levels are designed:
(A) situational introduction to stimulate interest
Novel course can stir up a thousand waves with one stone, better stimulate students' strong interest in learning and better lay a solid foundation for learning new knowledge. In order to reflect the close relationship between mathematics and life, I adopted the scene introduction of going to the bookstore to buy books, so that students can choose their favorite books, arouse their enthusiasm for learning, make students want to learn, and build a bridge between real life and abstract mathematics for students to continue learning.
(2) Step by step and explore new knowledge.
The formation of mathematical knowledge has inherent laws and strong logic, and there can be no jumps or loopholes. Take the following steps around the teaching focus:
(1) Ask students to make up a one-step calculation problem according to the given conditions. How to make it? Why is this happening? The meaning of decimal addition and subtraction is the same as that of integer addition and subtraction. Thereby breaking through the key points. Then the topics are divided into two categories: addition and subtraction, and further systematic learning.
(2) Let the students discuss the addition algorithm and get two methods: one is to convert 2.58 yuan and 3. 15 yuan into integers with "minutes" or "yuan, angle and minutes" for calculation. Question: Why are the vertical swing points aligned with points, angles, and elements? It is concluded that the same number is aligned, which lays the foundation for the principle of "decimal point alignment". The other is to calculate directly with decimals. The vertical pendulum must also be correct. Why do these two numbers swing like this? It is concluded that decimal addition, like integer addition, is to align and add the same numbers, while in decimal addition, the same numbers can be aligned as long as the decimal points are aligned. After further breaking through the difficulties and clarifying the calculation principle, let the students try to do another addition problem. On this basis, inspire students to compare the similarities and differences between decimal addition and integer addition. What is the key to decimal addition? Let students know the calculation method of decimal addition.
(3) When teaching the subtraction of decimals, I give students the initiative to explore knowledge completely, so that students can find problems themselves, sum up laws and solve problems, so as to achieve the purpose of letting students learn to learn, learn to learn and love learning.
(4) The practice of "try it" exposes students to the situation that there is a 0 after the decimal point, so that students know that it is generally necessary to simplify according to the nature of the decimal point.
(3) Deepen practice and consolidate new knowledge.
Exercise is an effective means to consolidate new knowledge, form skills, develop thinking and improve students' ability to analyze and solve problems in mathematics learning. In order to deepen students' understanding and application of the rules, and better understand that the meaning of decimal addition and subtraction is the same as that of integer addition and subtraction, I designed exercises at different levels to enable students to master knowledge and skillfully use them.
1, basic knowledge exercise: practice (oral calculation), judge and correct mistakes, exercise 2 1-3.
2. Application Exercise: Exercise 2 4-5
teaching process
First, situational import, stimulate interest
Students, do you like going to Xinhua Bookstore? In fact, there are many questions about mathematics in the bookstore. Here is one of them.
Second, step by step, explore new knowledge.
1, show example: Xiao Ming saw three books he liked in the bookstore, and the prices were as follows:
Harry Potter, Happy Mathematics and Crayon Shinchan
2.58 yuan 3. 15 yuan 5.79 yuan.
According to these conditions, can you ask some questions about one-step calculation?
2. Compared with the questions raised, they can be divided into two categories (addition and subtraction).
How much does it cost to buy a copy of Harry Potter and a copy of Happy Mathematics?
How much does it cost to buy a copy of Harry Potter and a copy of Crayon Shinchan?
How much is Crayon Shinchan more expensive than Harry Potter?
How much is a Harry Potter book cheaper than Happy Math?
3. Teach the calculation rules of decimal addition.
① Presentation: How much does it cost to buy a copy of Harry Potter and a copy of Happy Mathematics?
What method is used to calculate? How to form? (Blackboard formula) Why add?
(2) Discuss the calculation method:
Can you understand it according to what you have learned before? Students can discuss in groups first, and then communicate in the hall.
Calculate 2.58 yuan and 3. 15 yuan as integers in "minutes" or "yuan, angle and minutes" (write the calculation process on the blackboard and tell the final result).
Why are the points aligned, the corners aligned and the elements aligned when posing vertically? (The same numbers are aligned)
How to treat the algorithm of transforming the result into elements after calculation? (trouble)
Can you calculate directly with decimals? How to put it vertically? Why do you say that? Is this the same as that method? Align the same numbers as long as they are aligned in decimals. What is it? (Vertical bar of decimal addition on blackboard)
Can you do the second question? Finish it in the exercise book. Collective revision.
③ Discussion: Through the practice of the above two questions, what do you think are the similarities between decimal addition and integer addition in calculation? What is the key to decimal addition?
Summary: Decimal addition is the same as integer addition, and the same number of digits should be aligned. In decimal Djaafari, the decimal points should be aligned, starting from the low position; Whoever adds up to ten will be promoted to one. Finally, align the decimal point on the horizontal line and point the decimal point to the miles.
4. Teach the calculation rules of decimal subtraction.
① How to formulate the third and fourth questions? 5.79-3. 15 Can you calculate it? Try it yourself.
Who will remind you what to pay attention to in decimal subtraction?
③3. 15-2.58 You can try it yourself.
What's the difference between this question and the last one? What rules should decimal abdication follow?
④ What are the similarities between decimal subtraction and integer subtraction in calculation? How to calculate the decimal point of the result?
⑤ Summary: Decimal subtraction, like integer subtraction, is to align the same numbers. In decimal subtraction, the decimal points are aligned and subtracted from the low places; Who is not enough to reduce, just return one and do ten and then reduce; Finally, align the decimal point on the horizontal line and point the decimal point to the miles.
We only learned the calculation rules of decimal addition and subtraction by studying. What method do you think decimal addition and subtraction should follow? What is the difference (integer addition and subtraction)? (decimal point alignment)
6. Today, we learned the addition and subtraction of decimals, which are the contents on pages 8 and 9 of the book. Take a closer look when you get back.
7. Complete "Give it a try"
Students can finish it independently first, and then compare the results with the previous questions. What should I do with the 0 at the end of the decimal? Why?
8. What did you learn today?
Third, deepen practice and consolidate new knowledge.
1, complete the exercise 1. Talk about what should be paid attention to in calculation.
Finish the second question "Exercise".
Finish the third question of "Practice". How to calculate key communication questions 1 and 3?
2. Question 1, 2, 3.
3. Judgment and correction: (If the numbers are not aligned and the zero after the decimal point is not removed, subtraction can be made into three additions)
4. Do Exercise 2, Questions 4 and 5.
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