? But at the same time, we should also see that the textbook is not just a case. In practice, the teaching materials are the same because of the differences in regions and learning conditions. Teachers should not only respect textbooks, but also adhere to them. We should go into the textbook first, then jump out of the textbook and stand higher than the textbook, so as to overcome the limitations of the textbook to the maximum extent and give full play to the initiative and creativity of teachers.
The unit "two or three numbers divided by two numbers" is the teaching content of the second unit of the first volume of the fourth grade textbook published by Jiangsu Education Publishing House. It is arranged on the basis of dividing two or three digits by one digit, and the key point is the pen calculation of dividing two or three digits by two digits (some relatively easy two or three digits can be divided by two digits and can be calculated orally). There is a considerable leap from the division in which the divisor is a single digit to the division in which the divisor is a double digit. In order to facilitate students to master the written calculation of dividing two or three digits by two digits, the teaching materials are interspersed with corresponding oral calculation, estimation and solving practical problems.
? In the first class, I taught dozens (including hundreds) divided by dozens of oral arithmetic and vertical writing. An example is arranged in the textbook. Teaching two or three digits divided by dozens of quotients is the division of one digit. First calculate the quotient orally, then write vertically and arrange it in detail. Starting from the simplest division of dozens, it gradually develops into vertical calculation of dozens divided by dozens, hundreds divided by dozens, and non-integer three-digit divided by dozens, helping students gradually learn the thinking method of seeking quotient and initially learn to use vertical calculation division. I sorted out the overall arrangement of the textbook, such as 1: packaging the theme situation of Lu Zhanqi. The author combined that it was Teacher's Day and received many flowers on the podium, and immediately revised the situation:
? Class record:
First, check the import.
Teacher: Starting from today, we will enter Unit 2 (blackboard writing: division). What do you think of when you see division?
Health: I thought of the average score.
Teacher: Give me an example.
Health: I have six apples. I eat two apples every day. How many days can I eat?
Teacher: You can name a classmate to answer.
Health: Use 6 ÷ 2 = 3. Is there a (? ) 2.
Teacher: Where is division still used?
Health: …
Second, teach dozens divided by dozens of oral arithmetic
Teacher: Teacher, here are 60 flowers. Please send them to the office. If each student takes 20 flowers, how many students do you need?
Health: 60 ÷ 20 = 3 (bits)
Follow-up: Why 3?
Health: I think so. Because 20× 3 = 60, there are three twenties in 60.
Health: Because 6 ÷ 2 = 3 and 60 ÷ 20 = 3.
Follow-up: By contrast, what did you find?
Health: 6 has become 60, 2 has become 20, why hasn't 3 changed?
Teacher: Yes! The teacher also has such doubts! Who will explain?
Health: Because quotient plus 0 is 30, 20× 30 = 600, which is not equal to 60.
Teacher: Multiplication oral test, awesome! Any other ideas?
Student: Divider and divisor are multiplied by the same number at the same time, and the quotient remains the same.
Teacher: Yes! We will continue to learn the invariance of quotient later.
Student: Teacher, 60 means six tens, 20 means two tens, and there are three twos in six, so there are three twenties in six tens.
Third, teach dozens divided by dozens of vertical.
Teacher: If the teacher takes 96 flowers and each student takes 20, how many students do you need now? Please do it independently.
Show communication after life is completed.
Method 1: 96≈ 100, 100 ÷ 20 = 5 (person).
Ask the students by name: Why should 96 be regarded as 100?
Health: Because 96÷20 has a remainder, it is enough to regard 96 as 100.
Teacher: Does everyone take the same amount of flowers?
Health: The first four people all spend 20 flowers, and the last one takes 16 flowers.
Method 2: 96 ÷ 2 = 48 (person) and 96 ÷ 20 = 48 (person).
Student: Teacher, he is wrong. There can't be 48 people, because if there are 48 people, each person only needs 2 flowers.
Method 3: column vertical calculation 96 ÷ 20 = 4 (person) … 16 (flower)? 4+ 1 = 5 people
Follow-up: Why is quotient 4? Who should I write it on? What does 80 mean?
The teacher concluded: What's the difference between this teacher and the previous one? What is the difference?
Disclosure subject: Two digits or three digits divided by two digits.
Fourth, practice consolidation.
Independent attempt: 150÷30.
Check the calculation after completion.
……
Because of time, I didn't have time to finish the later contact, so I left it for the next class. )
Thinking after class:
When dealing with textbooks, we need to focus on two dimensions: one is the quantitative dimension, which mainly digs out the knowledge, ability and consciousness involved in textbooks from the breadth, expands textbooks from the extension, and pays attention to the multi-angle and multi-level connection between knowledge; The second is the qualitative dimension, which mainly excavates the concepts and viewpoints involved in the teaching materials in depth, adjusts the teaching objectives stipulated in the curriculum standards, and promotes the decline.
? In this lesson, the author made the following attempts:
? First, change the status quo.
? The situation of packaging Lu Zhanqi in the textbook was changed to sending flowers, which combined with the reality at that time and aroused students' interest. At the same time, the examples in the textbook and the questions in the test questions are connected in series in the same situation, and the scattered calculation exercises are integrated into the actual problem solving, which is close to the students' reality, conforms to the students' learning situation, mobilizes students' enthusiasm for learning and inquiry, and triggers students' mathematical thinking.
? Second, the transformation exercise
In short, changing the situation or changing the topic is not an end, but a means of teaching. The textbook presents us with an example of teaching, but it is not just an example. As a teacher, we should adapt to the needs of students and promote their thinking and ability.