Decimal addition and subtraction lecture notes

As a teacher, it is usually necessary to use class notes to assist teaching, which is helpful to improve teachers' language expression ability. How should I write a speech? The following is the speech of "Decimal Addition and Subtraction" which I carefully arranged, hoping to help everyone.

The draft of Decimal Addition and Subtraction is 1. First, talk about curriculum standards:

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.

Four, teaching procedures:

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 decimal addition and subtraction and integer addition and subtraction have the same meaning, 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

(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? This is 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 "Exercise". 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.

Lecture Notes on Addition and Subtraction of Decimals 2 I. Textbooks

1, teaching content

Decimal addition and subtraction is the teaching content of the first lesson of Unit 6, Volume 2, Grade Four, Standard Experimental Textbook of Mathematics Curriculum for Nine-year Compulsory Education and Six-year Primary School (People's Education Edition) (for example 1, for example 2 and "Doing One" on pages 95-97).

2. Analysis of teaching materials

The textbook of this lesson is arranged on the basis of students' recent understanding of the meaning and nature of decimals and their familiarity with integer addition and subtraction, which is the need of students' daily life and further study and research. Understanding and mastering the arithmetic and algorithm of decimal addition and subtraction is the basic mathematical knowledge, skills and methods necessary for primary school students. Compared with the old textbooks, this teaching content highlights that calculation is no longer boring, but chooses familiar and interested materials as the background of calculation teaching, which makes students feel that calculation learning is also lively and interesting, and enables students to understand the arithmetic of decimal addition and subtraction and master the basic methods of decimal operation when answering practical questions of decimal calculation. Moreover, decimal addition and subtraction and integer addition and subtraction are mathematically interlinked. For decimal addition and subtraction, students feel deja vu. The textbook firmly grasps this cognitive feature of students, deliberately does not give the calculation process of decimal addition and subtraction, and does not summarize the laws of decimal addition and subtraction, but deliberately guides students to migrate from the old knowledge of integer addition and subtraction to the new knowledge of decimal addition and subtraction. Using old knowledge is an important way for students to learn new knowledge.

3. Teaching objectives

According to the content of the textbook and the principle of "dealing with the relationship between inheritance and development", combined with the learning situation of students, I have determined the following teaching objectives.

(1) Contact students' real life and create situations. Let students explore the vertical writing of decimal addition and subtraction independently.

(2) Cooperation and communication, summarizing the general methods of decimal addition and subtraction, and understanding the principle of decimal point alignment.

(3) Be able to use what you have learned to solve some simple problems in life.

(4) Stimulate students' patriotic enthusiasm through teaching.

4. Emphasis and difficulty in teaching

(1) Teaching emphasis: decimal addition and subtraction.

(2) Teaching difficulties: decimal point alignment, that is, digit alignment.

5. Teaching preparation

In order to better implement the teaching focus and break through the teaching difficulties, I prepared two pictures of women's synchronized 10 meter platform diving in the 2004 Athens Olympic Games, projectors and other intuitive and vivid multimedia courseware before class.

Second, oral teaching methods

The teaching of decimal addition and subtraction is based on promoting students' development, creating situations closely related to real life, and allowing students to obtain written calculation methods of decimal addition and subtraction through their own exploration and cooperation. I try to embody the following three points in my teaching:

First, closely connect with life and create problem situations. With the help of the Olympic Games, a popular sports event for students, students' positive emotions and hobbies can be fully mobilized. Ask the students to ask questions in the women's 10 meter platform doubles final of the 2004 Athens Olympic Games, and stimulate their interest in learning decimal addition and subtraction. It is logical to introduce decimal addition and subtraction, so that students can enter problem-solving activities in the best state and actively explore the written calculation method of decimal addition and subtraction. Set up the problem situation of buying sporting goods in the consolidation and improvement link. It embodies the basic idea that mathematics comes from life and serves life. In this context, students can better understand the significance of learning decimal addition and subtraction and feel the value of mathematics.

Second, teachers boldly let go and students explore independently.

Because students have the basis of integer addition and subtraction, they make full use of this knowledge and experience in teaching and collect useful information by themselves. Ask questions and solve problems. In this series of learning activities, the teacher doesn't give any hints to the students, but reminds them to solve problems according to their existing experience, try to write vertically in decimal addition and subtraction, and realize the calculation method of decimal addition and subtraction in exploration. At the same time, through the exchange activities between teachers, students and students, the preliminary understanding will be raised to a new height, and the general methods of decimal addition and subtraction will be summarized to further understand the principle of decimal point alignment when columns are vertical.

Third, pay attention to the cultivation of students' ability to find and ask questions.

The premise of cultivating students' problem-solving ability is to let students gradually form a good habit of constantly discovering problems and asking questions. When teaching, we should make full use of the diving situation in the 2004 Athens Olympic Games to provide students with all kinds of information and space to find and ask questions. Let's first link the math problem with the medal list, watch the game with this problem, look for hidden math information, then find and put forward the math problem and finally solve it. Because these problems are put forward by students, students are more motivated to find ways to solve them.

Third, theoretical study.

In the guidance of learning the law, I use various guidance methods such as transfer, guidance, infiltration, comparison and feedback to highlight the characteristics of "four concessions": (1) Let students ask questions; (2) Mathematics makes students discover;

(3) Problems for students to discuss; (4) Evaluation involves students.

The above "four concessions" not only conform to the educational concept of the new curriculum, but also reflect the characteristics of independent inquiry classroom teaching.

Fourth, talk about teaching procedures.

In order to achieve the above goals, I designed the following teaching process:

(1) Create situations, review old knowledge and introduce new knowledge.

The courseware shows an integer addition formula: 7680+274 =

Teacher: Students, what is your formula? (Student answers)

Teacher: Yes, this is the integer addition formula we have learned. Can you do a vertical calculation quickly?

After calculating the result, how to prove that your calculation is correct?

Students calculate independently and choose a presentation.

Teacher: Students, who can tell me how you worked it out?

Point out a student talking about arithmetic.

The design intention is that the arithmetic and algorithm of integer addition and subtraction are the same as that of decimal addition and subtraction. Review and introduction clears the way for students to learn new knowledge by using old knowledge and summarize the calculation methods of decimal addition and subtraction.

Teacher: Well, on the basis of integer addition and subtraction, today we are going to learn the addition and subtraction of decimals (blackboard writing topic).

Q: Students, do you have any questions about the addition and subtraction of decimals? The students answered.

The design intention is to let students study with questions, and the task is clear.

(The courseware shows the situation map)

Teacher: Look, this is the final picture of China divers' synchronized 10 meter platform diving in the 28th Athens Olympic Games in 2004. How do you feel after reading it?

The students answered.

Teacher: It is also the athletes of our country who won glory for their country at the Athens Olympic Games and showed themselves and the spirit of courage to fight in front of the people of the world. Isn't this an example for us to learn?

1, exchange information, courseware display performance statistics.

Teacher: Students, after reading this report, do you know how to determine the gold medal of synchronized 10 meter platform diving?

The students answered.

Teacher: What mathematical information did you find from the final results?

The students answered.

2. Ask questions and solve problems.

Teacher: Based on this information, what math questions can you ask?

Ask the students to write down the questions in the prepared notes.

Then show the questions put forward by the students on the blackboard.

The creation of design intention situation not only cultivates students' ability to collect information, organize information and ask questions. It also stimulated students' enthusiasm for learning and patriotic feelings, infiltrated the connection between mathematics and life, and laid the foundation for developing this course.

(2) Explore independently and explore ways to solve problems.

Teacher: You asked so many questions, which ones were solved by addition and which ones were solved by subtraction?

1, everyone has raised so many questions, will they be solved? Work in groups, first choose an addition problem from these problems, then choose a subtraction problem, and try to calculate vertically. It's done. Tell me how to do it. Let's get started.

(1) exploration attempt.

The design is intended to give students the opportunity to solve problems independently, and through the process experience, the calculation is clear and the rationality of the calculation method is realized.

(2) Reporting and communication.

① Decimal addition

Teacher: Let's talk about the problem solved by addition.

53.40+58.20 =11.60 (minimum) 53.40

+58.20

1 1 1.60

First, align the numbers, and then add them in low order, where the percentile is written as 0, the decimal is written as 6, and each digit is full of ten. Enter one into ten ... Finally, align the decimal point vertically so that the decimal point is at the midpoint of the result.

Teacher: Is he right? Who has anything to add?

Teacher: What do you think is the difference between the two results? Usually, the calculation result with 0 after the decimal point should be simplified. So it should be written as 1 1 1.6. Who wants to talk about the addition problem you solved? (including the problems solved by multi-step addition calculation, you can master them flexibly with the students' speeches. )

② Decimal subtraction

Teacher: How did you solve the problem of subtraction? Tell me about your calculation process.

53.40-49.80 = 3.6 (points)

53.40

-49.80

3.6

Align the decimal point first, and then subtract it from the low order. If the percentile is 0 and the decimal point is 4 minus 8, which is not enough, then subtract 14-8 from the single digit, and the decimal point in the decimal point is 6, ... Finally, align the decimal point in the vertical position with the midpoint of the result. 3.60 is simplified to 3.6.

The design intention is to guide students to better understand and form the calculation rules of "decimal point alignment". They should not judge the correctness of the vertical form only by "whether the decimal point is aligned", but should guide students to analyze it in connection with existing experience. Considering the specific number, we can also analyze the meaning of decimal according to the experience of integer addition, and align the numbers of the same counting unit vertically with the columns, which is the most convenient for calculation. It can also be judged by estimation. In terms of teaching methods, I will let students explore the algorithm independently first and initiate discussions according to the situation.

(3) Summarize the algorithm, show the courseware and read it by all students.

Teacher: What should I pay attention to when calculating the addition and subtraction of decimals? Tell your peers what you think first.

(2) the whole class communication, teachers and students * * * with summary.

When the column is vertical, the decimal points should be aligned first, that is, the same numbers should be aligned. Then add or subtract from the low order, and when calculating the addition, which number is full of ten will advance to the previous one. When calculating subtraction, which digit is not enough to be subtracted is subtracted when the previous digit is ten.

Teacher: What do you think of decimal addition and subtraction is similar to addition and subtraction?

Teacher: We can also say that decimal addition and subtraction are calculated in the same way as integer addition and subtraction. It should be noted that the decimal point in the vertical position should be aligned and added to the midpoint of the result. The zero after the decimal point in the final result should be removed.

Teacher: Yes, the calculation results should be simplified. Let's summarize the written calculation method of decimal addition and subtraction. I hope everyone can pay attention to these in future calculations.

The design intention is to cultivate students' mathematical comparative thinking through students' cooperation and exchange, as well as the comparison and induction of decimal addition and subtraction algorithm and integer addition and subtraction algorithm. It is of universal significance to understand mathematical laws in comparison, and there are different forms of expression in the process of use.

(4) Checking calculation

Teacher: the calculation of decimal addition and subtraction is easy to make mistakes. Is there any way to check the calculation results? The teacher will remind you again if there is any difficulty. )

(5) reading doubts.

The design intention is to cultivate students' self-study ability through reading; The process of asking questions is actually a process of sorting out and digesting new knowledge and constructing knowledge independently.

(3) Set the situation and practice.

1, Ph.D. in Mathematics, let's see who has high medical skills.

①2 1.6+5.47=76.3② 17.23+2.77=20.00③49.7-5.7=440

2 1.6 17.2349.7

+5.47+2.77-5.7

76.320.00440

2. Calculate the following questions and check them.

① 12.47+8.23=②2 1.566.7=③8.24-3.56=④4 1.2- 15.6=⑤30- 15.8=

3. See which group can finish quickly and accurately.

Liangliang is a child who loves sports very much. On Sunday, his father took Liangliang to the sports shopping center to buy things. (Courseware display)

Design intention exercises have various design forms and distinct levels. It not only consolidates students' computing ability, but also cultivates students' application ability. In this link, students are also allowed to conduct self-evaluation and mutual evaluation among classmates. Greatly improved the enthusiasm of students to learn.

(4) class summary

What did you gain from today's study?

Decimals are indispensable partners in our life and study. I hope that students will pay more attention, observe more and solve the math problems around them with what they have learned.

Five, say blackboard writing design

As another form of classroom teaching language, blackboard writing should be enlightening, instructive and applicable. In order to highlight students' dominant position, concentrate on learning and solve knowledge difficulties, the blackboard writing in this lesson not only pastes students' questions, but also shows the vertical writing of decimal addition and subtraction. This arrangement is conducive to mobilizing students' learning enthusiasm and improving teaching efficiency.