Analysis of the trial lecture script "Using Letters to Represent Numbers" for the 2017 Primary School Mathematics Teacher Recruitment Interview

During the interview, lectures or lectures are used to conduct the examination. At the same time, in many areas, after the lecture examination, there will be Structured interview questions appear. So, the following is an analysis of the trial lecture notes on "Using Letters to Represent Numbers" that I compiled for you. You are welcome to read and browse.

1. Teaching materials

"Representing Numbers with Letters" is the fifth grade mathematics volume "Simple Equations" of the People's Education Press's "Compulsory Education Curriculum Standard Experiment Textbook" 》Teaching content of the first lesson. This is the starting point for students to learn preliminary knowledge of algebra, and is also the basis for learning equations, inequalities, functions and other knowledge.

Using letters to represent numbers is relatively abstract for primary school students. The numbers in students' minds are concrete and definite, while the numbers represented by letters are abstract and variable. This is a leap in understanding. The process from expressing numbers with numbers to expressing numbers with letters is a long process that requires students to go through a lot of activities and accumulate rich experience.

In the past, in teaching, we often did not delve deeply enough into the meaning and function of letters representing numbers, and students did not have sufficient experience. The "Curriculum Standards" clearly point out: Let students experience and understand mathematics in real situations. Therefore, in this lesson, I focus on letting students experience and understand the meaning and function of using letters to represent numbers repeatedly in different situations as the core of teaching, focusing on experience and understanding.

Teaching objectives:

(1) Create different situations to promote students to understand the meaning of using letters to represent numbers, and to know the different value ranges of numbers represented by letters.

(2) Ability to communicate using letters to represent numbers in specific situations.

(3) Penetrate interval thinking.

(4) Feel the simple beauty of mathematics.

Teaching focus: Understand the meaning of using letters to represent numbers.

Teaching difficulties: Understand the use of letters to represent uncertain numbers, and know the different value ranges of letters (a number, a part of a number, or any number).

2. Preaching method

There must be a method for teaching, but there is no fixed method for teaching. Only the method will be effective. According to the characteristics of the teaching content of this course and the characteristics of students' thinking activities, I adopted the teaching method of situational teaching method and combination of lecture and practice. The exploration process follows: from concrete to abstract, from individual to general, and from general to individual.

3. Talking about student learning

First of all, teachers create a good environment and guide students to start with life content they like, know and are familiar with, so that students can learn by themselves in a specific environment. Unconsciously, we establish that letters are in life and around us. Through a series of activities, students cooperate, communicate, and explore independently to further understand that letters can not only represent a specific number, but also represent changing numbers. The same letter The range of numbers represented in different situations is also constantly changing. Then through various connections, they are transformed into problem-solving strategies to explore the different abilities of students at different levels, thereby cultivating students' ability to explore problems, communicate and solve problems.

4. Teaching procedures:

The entire teaching process is arranged in five links.

Part 1: Understand the meaning of using letters to represent numbers, and know the different value ranges of numbers represented by letters. This is the focus and difficulty of this lesson. The "New Curriculum Standards" points out: Mathematics teaching is the teaching of mathematical activities and is a process of interaction and joint development between teachers and students and between students. Therefore, in the first session, I preset two activities, one activity is a different level of experience

Activity 1: Promote students to understand that letters represent a certain number.

1. As soon as the class starts, the courseware will show different pictures, so that students will know through observation that letters can not only represent the names of things, but also can be used to represent numbers, thereby introducing a new lesson.

2. Take Example 1. After observation, we found that these symbols and letters can be used to represent numbers. Students have been exposed to using symbols such as ■, ▲, and ● to represent numbers before, and using letters to represent numbers is new knowledge. The purpose of solving Example 1 is to once again realize how to use letters to represent a certain number.

Activity 2: Promote students' understanding that letters represent uncertain numbers, and encourage students to understand the different intervals of letters representing numbers in specific situations.

Place a square? List the multiplication formulas containing letters

The courseware is presented one by one:

After students write the corresponding calculations according to the number of squares they have placed, The teacher asked: "A square like this can be placed forever. Can you use more calculation formulas to express the number of small rods used to place different numbers of squares? Then let the students continue to write the calculation formulas, with the purpose of giving students an initial experience of this There are never enough calculations to be written, so that students can understand the superiority of using letters to represent numbers, and then let students think of ways to use one formula to summarize all calculations, that is, to express them with calculations containing letters. Let students understand that letters can not only represent a A specific number can also represent a changing number.

Then, guide students to observe and discover that: the number of squares is constantly changing, and the number of small rods is also constantly changing, but it takes a The four small sticks remain unchanged, or in other words, the relationship that the number of small sticks is three times the number of squares remains unchanged. This is just as the German mathematician Kepler said: Mathematics is the study of unchanging relationships in ever-changing situations.

Finally, the teacher deliberately asked: ?a? What numbers can be represented here? Can it be a decimal? Can it be a fraction? It is for students to initially understand the numbers represented by the same letter in different situations. The scope is constantly changing. The teaching of this knowledge point aims to guide students to once again explore the relationship between using letters and formulas containing letters to express numbers and quantities. At the same time, organically penetrate the idea of ????functions and understand the necessity of using letters to express numbers

2: Explore the calculation formulas that use letters to represent relevant graphics, and promote students to understand the different intervals of numbers represented by letters in an abstract form.

First of all, the teacher asked: How to calculate the perimeter of a square? (Students answer, the teacher shows the formula for calculating the perimeter) ?How to calculate the area of ??a square? (Students answer, the teacher shows the formula for calculating the area)

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Next, the courseware provides the letter representation requirements for the formulas for the perimeter and area of ??a square.

Then, guide students to use letters to express these two formulas according to these requirements. (Student answer: writing on the blackboard: C=a?4, S=a?a)

This level of teaching aims to guide students to use letters to represent calculation formulas for graphics they have learned, and to experience the role of letters again .

Session 3: Teaching the abbreviation method of multiplication expressions containing letters. < /p>

Students answer the abbreviated formulas of c=a?4 and s=a?a (the teacher writes on the blackboard following the above formula).

2. Consolidate the application

Working in groups, one person will ask the question and the other will answer the question

3. Use letters to represent the learned operation laws.

4. Use alphabetical formulas to find the perimeter and area of ??a square.

First let students talk about which conditions they must know in order to find the area or perimeter of a square, and then let the group Students work together to first measure the side lengths of the square they have placed, and then use formulas to find its area and perimeter. The purpose is to make students initially perceive that letters can not only represent changing numbers, but also the range of numbers they represent is also constantly changing. Students can complete it independently, with emphasis on writing format

Session 4: Summary of the whole lesson

Session 5: Expansion and extension

Courseware provided:

⑴The earliest records of humans using letters.

⑵Introduction to the father of algebra - Veda.

This link will infiltrate mathematics culture in a timely manner, aiming to enable students to understand relevant mathematics history knowledge and at the same time receive ideological education and emotional influence, so as to better promote student development.

Session 6: Swimming through the Olympic maze? (Show the courseware one by one)

First, use letters and formulas containing letters to represent the journey from the entrance to the smart house, boat pavilion, and music respectively. Bar's journey. Let students talk about why three sections of distance are represented by different letters, and then understand that different numbers in the same calculation are represented by different letters.

Next, let’s come to music. What is going on in the music bar?

Use letters and expressions containing letters to represent the entire "Counting Frogs" children's song. (?Try it?1)

Go to Fuwa Square (True or False Question)

Finally, go to Wisdom Palace. There is a mural in the Wisdom Palace. Ask students to talk about the connection between the picture above and 7a below. If you remove the 7 volleyballs on the top, what kind of picture can you think of? The purpose is to make students understand life. Many meaningful examples can be represented by 7a.

Einstein said: Interest is the best teacher.

?In view of the fact that using letters to represent numbers is relatively abstract and boring, the situation string of "Happy Tour" was specially designed to guide students to comprehensively apply the knowledge and skills they have learned and improve problem-solving through exercises with lively forms and diverse contents. ability, and experience the fun of solving problems, stimulating the love of mathematics.

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