Topic 1: A preliminary understanding of Division (1) (a)

Teaching content:

Page 40 of the textbook, example 1, example 2, "do" on page 4 1 or above; Exercise 12, questions 1 and 2.

Teaching purpose:

1. Make students understand the meaning of division and "average score" and master the method of "average score" initially.

2. Know how to divide a number into several parts, find out how much one part is, and calculate by division.

3. Learn how to read and write division formulas.

Prepare teaching AIDS and learning tools:

The teacher prepares 6 peaches, 3 plates or pictures, 12 (8 balls and 2 boxes can be prepared if possible). Each student prepares 8 cubes, 12 sticks and 15 triangles.

Teaching process:

The teacher briefly stated first: We learned addition, subtraction, multiplication and division. Do you remember what they mean? Today we are going to learn a new calculation method-division.

First, the new lesson

1. Let students know the meaning of "average score" through physical demonstration.

Before the teaching example 1, teachers can let students directly perceive the meaning of "average score" through the following activities.

The teacher took out six pencils and invited three students to the podium. The teacher explained that six pencils should be given to three students, and everyone should get the same number. Please pay attention to the process of dividing.

First, everyone is divided into 1. The teacher asked, "Are you finished?" After students answer, each student will be divided into 1 branches. The teacher then asked, "Have you finished writing?" (the points are over. )

The teacher asked the class to observe: How many skills did the three students acquire? (Everyone gets 2 sticks. ) Does everyone get the same amount? (as much. )

Teacher writes on the blackboard: Just as much.

Then the teaching example 1 asks students to take out eight small cubes (or other objects) prepared and put them on the desk. Then, according to the teacher's method of dividing pencils just now, divide the eight small cubes into four parts, and each part should be divided into "equal amounts". Let each student put a swing, and then actually divide it into several points. Teachers patrol to understand the situation of students, especially to see the specific operation process of students.

After the students were released, the teacher asked a good student to demonstrate the grading process in front of the blackboard. (Student: First put 1 cube in each serving, and then put 1 cube in each serving. That's the end. )

Teacher's question: Do you get the same amount per share? How many are there in each serving?

Then the teacher emphatically pointed out: like this, each score is the same, which is called "average score"

Write on the blackboard next to "as much": average score.

The teacher asked: How to use the word "average score" to simply describe the fact that it is divided into eight small cubes? If the students have difficulty in answering, the teacher can enlighten them appropriately: How to divide the students into eight small cubes? What do you mean equal per share? On the basis of students' answers, the teacher summed up that there are eight small cubes on it, so it can be said that "the eight small cubes are divided into four parts on average." Ask again: How many copies each? (2.)

2. Through demonstration and students' operation, students can master this division method and know that "divide a number into several parts on average and find out how much one part is" is calculated by division.

Teaching example 2. Show "Divide six peaches equally in three plates. How many are there in each plate?" While dictating the topic, take out pictures of six peaches and three plates and post them on the blackboard. At the same time, students can also take out pictures of six peaches.

Question: What does it mean to divide six peaches equally among three plates? (that is, put the same amount on each plate. )

Put six peaches evenly on three plates. How should I put it?

After the students answer, the teacher demonstrates the process of average score. When demonstrating the average score, it should be emphasized that in order to make each dish have the same number of peaches, you should first put three peaches in each dish. Ask questions and ask students to set up their own learning tools step by step under the teacher's demonstration.

Put 1 on each plate. Is it finished? (number)

Play each set again 1. Is it finished? (the points are over. )

How much do you put in each plate? (2.)

Is it the same quantity? A: Yes. )

What do you call this method of dividing items? (average score. )

Teacher's summary: Divide the six peaches into three equal parts, each with 2 peaches.

Q: What do you mean by dividing eight cubes into four parts and six peaches into three plates?

According to the students' answers, the teacher summed it up: dividing items like the above is a question of dividing some items into several parts on average and how much they cost. In mathematics, we need to use a new method-division to calculate.

Blackboard: division

Then the division symbols are given: in the past, when we learned to add, subtract, multiply and divide, we used the operation symbols "+","-"and "×". The operation symbol of division today is "∫". (blackboard writing:) is called division. When writing, draw a horizontal line first, and then go up and down a little bit. The horizontal line should be straight and the two points should be aligned.

Question: "Divide six peaches into three parts equally. How much is each part?" How to list the division formula of this problem? (speaking and writing. )

How many peaches do you want to share? Write "6" before the division symbol. Writing on the blackboard: 6.

Divide the sixth grade into several parts. Write "3" after the division symbol.

How much is each? Write "2" after the equal sign.

Description: The formula "6 ÷ 3 = 2" is called the division formula, which means that six peaches are divided into three equal parts, each of which is 2.

Guide students to read the formula: 6 divided by 3 equals 2.

Ask the students to say the meaning of the equation.

Then ask the students to open their books and guide them to look at the picture of children splitting peaches in Example 2. Let the students talk about the meaning of the picture first, and then guide the students to separate the remaining peaches in the picture on the right with a line.

Recess activities.

Second, classroom exercises.

1. Complete the exercise in "Getting Started" on page 4 1.

Question 1 (1), let the students look at the question first and say the meaning of the question. Then let the students take out the 12 stick and start swinging. When students pose, the teacher should remind them to think about how to divide them. At the same time, we should pay attention to patrol and correct the incorrect division in time. Then ask the students to complete the division formula according to the result of pendulum. Say the meaning of each number in the division formula.

Question (2), let the students see the problem by themselves first; Put a stick and write the division formula independently. Teachers should pay special attention to whether the students' operations are correct and whether the formulas are wrong. Then modify it collectively. When revising, you can selectively let the students who have made mistakes talk about it and discuss why they are wrong. Students can also compare (1) and (2) to see their similarities and differences. Make it clear to the students that although they all scored 12 on average, the scores are different, so the results are different. So the division formula is not written exactly the same.

Question 2. Let the students see the pictures clearly first. How many balls should I divide? How many boxes are divided? How to divide it? Then, let the students imitate the method of connecting lines in Example 2, and actually connect lines to show the process of division. Students who have difficulty connecting can also be asked to use school tools. Finally, write the formula in the book. When revising, read the formula by name and say the meaning of the formula.

2. Do exercises 12 1 and 2 questions.

In the question 1, the teacher first explains the meaning of the question, and then asks the students to write the division formula of the left question. Ask the students to read the division formula in a low voice, tell the meaning of the division formula, and then patrol the teacher in class to review. Let the students do the questions on the right independently and correct them collectively.

Question 2, the teacher explains the meaning of the question and takes the students to complete "8 ÷ 2 = □". Let the students read the formula in a low voice first and think about the meaning of the formula by themselves. How many deltas should they take out and how to divide them? Let the students fill in the numbers on the basis of the operation. Teachers ask questions and patrol. Let the students speak their own thoughts when reviewing. "10 ÷ 5 =□" and "15 ÷ 3 =□" allow students to complete independently. Teachers patrol and correct mistakes in time when they find them. Students who study well are also allowed to write grades without operation. For most students, it is still required to write numbers on the basis of operation. When reviewing, students at different levels can talk about their own ideas, thus mobilizing students' enthusiasm for learning.

Three. abstract

Today we learned to divide some items into several parts, find out how much each part is, and calculate by division; I also learned how to read and write the division formula. I hope the students will review well, and we will learn new knowledge next time.