First, the teaching objectives

1. Knowledge and skill goal: master the method of expressing numbers by letters, and learn to use abbreviations and abbreviation multiplication in formulas containing letters.

2. Process and Method Objective: Through classroom exploration and cooperative communication, we can initially understand the advantages of using letters to represent numbers and understand the functions of using letters to represent numbers. Improve the understanding of the operation law of letter representation.

3. Emotional Attitude and Values Goal: Understand the meaning of numbers expressed by letters, develop the sense of numbers and symbols, and feel the beauty of simplicity in mathematics.

Second, the importance and difficulty of teaching

Key point: I understand the meaning of using letters to represent numbers, and I can express simple quantitative relations with formulas containing letters.

Difficulty: Use a formula containing letters to correctly express the relationship between two quantities.

Third, teaching preparation.

Multimedia courseware, student question list.

Fourth, the teaching process

(1) Game import

Ask the students to guess how many frogs may be hidden in the water. For example, "A frog has a mouth, two eyes and four legs; ……"。 And ask: classmates, can you find any rules? Let the students think and answer.

(B) the new curriculum teaching

1. Understand the meaning of numbers represented by letters.

The teacher gave three groups of questions for example 1 and asked: The number of groups on the screen is arranged according to certain rules. Did you find it? Please think for yourself first, and then finish it on the list.

(1) Students understand the meaning of the topic, and the teacher guides the students to clarify the requirements of the topic.

(2) Students try to find out the rules and write unknown values. And discuss and communicate in groups.

The teacher guides the students to describe the law of each small question or the meaning of known conditions in their own words.

(3) Ask students to independently calculate the numbers expressed by numbers or letters and communicate with the whole class.

(4) The teacher asked: What are these three questions expressed in numbers or letters? Have you ever seen examples of numbers represented by symbols or letters?

(5) The teacher asked: What does the following A mean?

1+a=30 1+a