1, combined with specific conditions, experience the application of common multiple and minimum common multiple, and understand the meaning of common multiple and minimum common multiple.

2. Explore ways to find common multiples. We will use enumeration and other methods to find the common multiple and the minimum common multiple of two numbers. We will find the least common multiple by multiplication and subtraction.

3. In the process of exploring the method of finding common multiple, cultivate students' analytical and inductive ability and cultivate their innovative spirit.

Emphasis and difficulty in teaching

Explore the method of finding common multiples.

teaching tool

courseware

teaching process

First, review old knowledge and introduce new lessons.

1, write a multiple of 2 within 20.

2. Write all the factors of 20.

3. What is the smallest factor? What is the biggest factor?

4. What is the minimum multiple of a number? Maximum?

Teacher: We have learned about factors, multiples, the greatest common factor and so on. Today, let's study together? Find the least common multiple? .

Find the least common multiple.

Second, explore exchanges and gain new knowledge.

(1) Go to the Children's Palace. △

1, creation? Go to the Children's Palace? Situation.

2. Please say something? Go every two days and every four days? How to understand.

3. Guide students to explore? When will they go to the Children's Palace at the same time? Solution strategy.

(1) Circle the days when they went to the Children's Palace with different symbols on the calendar.

(2) Write down these figures and see what features they have: the days when naughty people go to the Children's Palace are all multiples of 3, and the days when young people go to the Children's Palace are all multiples of 5.

(3) Observe the characteristics of the days when two people go to the Children's Palace at the same time. It is concluded that these numbers are common multiples of 3 and 5, and the concepts of common multiple and minimum common multiple are put forward.

(2) fill in.

1, find the multiple of 4 and 6.

(1) Students search independently, and teachers patrol the classroom.

(2) Feedback the results.

2. Find the common multiple of 4 and 6.

(1) In these numbers, it is marked as? △? It's marked again? What are these numbers? What numbers are they?

(2) It is both a multiple of 4 and a multiple of 6. Can you give it a name?

Least common multiple of 3, 4 and 6

(1) What is the smallest of these common multiples? Can you give it a name?

(2) Is there a greatest common multiple? Why?

4. Summary: Two numbers, the common multiple is called the common multiple of these two numbers, and the smallest is called the least common multiple. The number of common multiples is infinite.

Third, practice.

Please fill in the questions 1, 1 and 2 independently, and then organize students to communicate, and the teacher will give necessary guidance. The purpose of these two questions is to let students further master the basic method of finding the least common multiple of two numbers.

2. Question 3, find the least common multiple of the following groups. Now ask the students to practice independently, and then talk about your findings. Encourage students to express their findings in their own language.

3. Question 4, let the students solve it by themselves and guide some students who have difficulties, first understand? Trains run every 4 minutes and every 6 minutes? How to understand, then guide them to explore problem-solving strategies, and gradually let students understand that the process of solving problems is to find the common multiple of 4 and 6,12,24, etc.

Fourth, do you know?

You can also use multiplication and reduction to find the least common multiple.

Verb (abbreviation of verb) summary.

What is the least common multiple? How to find the least common multiple?

homework

Finish the exercises after class.

Total score and least common multiple teaching plan (2) Teaching objectives

1. Knowledge and skills: Solve the concepts of common multiple and minimum common multiple, and understand and master the method of finding the minimum common multiple of two numbers.

2. Process and method: enable students to explore and understand the concepts of common multiple and minimum common multiple, find the method of minimum common multiple of two numbers, and cultivate students' migration ability and ability to analyze and study problems.

3. Emotion, attitude and values (educational goal): in the learning process discussed by teachers and students, stimulate students' interest in learning and cultivate students' good study habits.

Emphasis and difficulty in teaching

Emphasis and difficulty: the method of finding the least common multiple of two numbers.

teaching process

(a), the team leader report? Pre-research How to find the least common multiple of 3 and 2 in the case of completion?

Step 1: The multiple of 3 is: ()

The multiple of 2 is: ()

Step 2: The common multiples of 3 and 2 are: ()

Step 3: The least common multiple of 3 and 2 is: ()

(2) Group discussion? Pre-research

1, ask the groups to solve their mistakes and talk about their own methods;

2. Ask the students to say:

(1) What are common multiples and minimum common multiples?

(2) What is the common multiple of two numbers?

(3) Introduction: Today we will discuss the least common multiple (blackboard writing topic).

Show examples of books 1. A wall brick is 3 centimetres long and 2 centimetres wide. If a square is paved with this kind of wall brick (all the wall bricks used are a whole piece), how many decimeters can the side length of the square be? What is the smallest decimeter?

1. Please take a closer look at the decoration requirements of Xiaoming's house. What valuable information did you get?

① Use this wall brick with a length of 3dm and a width of 2dm to pave a square.

(2) The wall brick used must be a whole block, and it cannot be cut by half.

③ The question is: How many decimeters can the side length of a paved square be, and what is the minimum?

2. Let's first study how many decimeters the side length of a square can be. You have a solution to this problem.

Is there a problem?

3. Learning tools: a rectangular piece of paper, 3 meters long and 2 meters wide.

Hands on practice.

(1). Requirements:

(1) Use rectangular pieces of paper instead of wall tiles to make a square.

Talk to your deskmate and tell me the side length of your square.

(2) Exchange of query results.

(1) I put two rectangles in the first row and put these three together to form a side length.

6dm squared.

(2) I put four rectangles in the first row, and put six rows like this to spell out a side length.

12dm squared.

Can you spell a different big square?

Student discussion:

(3) If we have enough small rectangles, can we spell squares with other sides?

(4) For such a small rectangle, the side lengths can be spelled as 18dm, 24dm and 30dm.

Square? Discuss it in the group.

(5) How many large squares with different sides can we spell out from a rectangle with a length of 2dm and a width of 3dm? Tell me why.

(6) Can such a rectangle be made into a square with a side length of 8dm? Tell me why.

1 No. Because 8 is a multiple of 2, not 3, you can't spell a square with a side length of 8.

② Practical hands-on operation.

(7). What is the smallest length of all squares? How did you know?

(8) Summary and promotion: What have you gained by solving this problem?

① Finding the least common multiple of 3 and 2 can also be expressed by the method of set circle.

(2) the whole class communication, writing on the blackboard.

Multiple of 3

A multiple of 2

Can the edge length be 6 dm, 12 dm, 18 dm? Square,

The smallest square side length is 6 dm.

6, 12, 18,? Is the common multiple of 3 and 2, which is called their common multiple.

Where 6 is the least common multiple, which is called their least common multiple.

4. Test you: Solve problems with newly learned knowledge: Complete P89 and start work.

5. Teaching Example 2: How to find the least common multiple of 6 and 8?

(1) Students finish independently and communicate with the whole class.

(2) Students' communication methods are (courseware demonstration during communication).

(1) enumeration method: first find the multiple, then find the common multiple, and finally find the least common multiple.

Such as multiples of 6: 6, 12, 18, 24, 30, 36, 42, 48,,,

Multiples of 8: 8, 16, 24, 32, 40, 48,,,

Common multiples of 6 and 8: 24, 48,,,

Least common multiple of 6 and 8: 24

(2) The diagram is also very clear.

Which multiples of 36 are multiples of 8?

Do you have any other methods? Discuss with your classmates.

The teacher introduced:

① Double method of large numbers: 8, 16, 24,

Least common multiple of 6 and 8: 24

② factorization method: 8=2? 2? 2

6=2? three

The least common multiple of 8 and 6 = 2? 2? 2? 3 = 24

The least common multiple of 8 and 6 includes the product of the common prime factor of 8 and 6 and their unique prime factor.

6, through observation, think about:

What is the common multiple of two numbers?

What is the relationship between the common multiple of two numbers and their minimum common multiple?

Will you find the least common multiple of two numbers in the exam?

Read the book P90 and do it: Find the least common multiple of each group number below and see what you find.

3 and 6 2 and 8 5 and 6 4 and 9

7. Communicate your findings: If two numbers are coprime, multiply them directly and find the least common multiple; If two numbers contain multiples, the larger number is the least common multiple of the two numbers.

8. I can quickly say the least common multiple of each group number.

8 and 9() 24 and 8 () 30 and 5() 4 and 12() 36 and 4() 48 and 6 () 17 and 13() 14 and15 ().

(4) Strengthen application and consolidate practice.

1. There is a pile of sugar, 4 plots and 6 plots, all of which are counted just right. This pile of sugar at least

How many?

2. If the total number of these students is less than 40, how many may there be?

Aunt Li watered the roses and Clivia at the same time. She should water the two flowers at the same time in a few days.

Knowledge application: practice

Task:

Homework: 72 pages of exercises 17, 10 and 1 1.

(5) Class summary: What have you gained from studying this lesson?

blackboard-writing design

least common multiple

Common multiple: a multiple shared by two numbers.

Least common multiple: the smallest multiple of two numbers.

Looking for what? Least common multiple? Method:

1, in general:

Write the multiple of one number first, then the multiple of another number, and find the least common multiple of two numbers from the common multiple of two numbers.

2. Special circumstances:

(1) When two numbers are multiples, the least common multiple of these two numbers is a larger number;

② When two numbers are prime numbers, the least common multiple of these two numbers is the product of these two numbers.