Teacher: Classmates, have you finished the Mid-Autumn Moon Cake? (Student Qi answers: Finished) My teacher hasn't finished eating the moon cakes. Today, I specially brought a piece of moon cake and wanted to share it with you. Who wants to eat? (I ...)

Second, the professor's new knowledge:

1, professor 92 cases 1:

Teacher: I want to share this moon cake with Pei Xiaofen. Pink, how can I share it with you fairly? Can you share a point of view?

Health: OK. (raw cut moon cakes)

Teacher: Is it fair for her to divide the moon cakes like this? (The teacher shows the results of "dividing moon cakes" and prepares two dialogue schemes: ① If the students can divide the moon cakes equally, ask all the students, "Why do you think she got a fair share?" ② If students can't distribute moon cakes equally, ask all students, "How can we share them fairly?" -Purpose of the conversation: introduce the "average score" and understand the meaning of the score. )

Teacher: Luo Jiayang, do you think he gets a fair share?

Health: unfair.

Teacher: Why?

Student: Because she has a large share and a small share.

Teacher: What do you think is fair?

Health: Two copies are the same size.

Teacher: How can we divide them into the same size?

Health: Cut evenly from the middle.

Teacher: That's good. Applause.

Health: (Applause)

Teacher: The teacher operates the courseware-demonstrating "dividing moon cakes".

Teacher: teacher's blackboard writing: divide a moon cake into two parts on average, which means that one part is like this.

Teacher: Please observe the difference between ""and the numbers we have learned before.

Student: There is a number above and below this number, and there is a horizontal line in the middle.

Teacher: Good point. Let's applaud him. Numbers like this are the scores we are going to study today. (blackboard writing topic)

Teacher: (Introduce the names of each part of the score to the students) This horizontal line is called the fractional line, the number above the fractional line is called the numerator, and the number below the fractional line is called the denominator. (blackboard writing)

1 molecule

——————————— Fraction line

Double denominator

Teacher: (Fan writes scores) Have you noticed the order in which I write scores? (Instruct students to write scores according to the meaning of scores) Luo Jiayang divided the moon cakes into two parts on average. Where did you find "2"? (below the fractional line-denominator) refers to such a copy. Did you find "1"? Where is it? (Above the fractional line-numerator. )

(Guide students to master: divide it into several fractions as denominator, indicating that such fractions are numerators. )

2, professor 93 cases 3:

Teacher: (continuing the conversation) Just as Pei and I were about to eat moon cakes, two more students came, so we had to divide this moon cake again. Who can tell us how to divide it?

Teacher: (The teacher asked a student to "divide the moon cakes" again. Because students have such a life experience, it is not difficult to score four, and it is still necessary to emphasize "average score". )

Teacher: The teacher operates the courseware-demonstrating that moon cakes are divided into four parts on average.

Guide the students to say that the moon cakes are divided into four parts on average and write them on the blackboard. Let the students try to write scores in the exercise book, and the teacher will check the students' writing. )

Teacher: Just when the four of us were going to eat moon cakes, four more students came, and we were going to divide the moon cakes again.

Teacher: (refers to asking students how to mark-)

Teacher: The teacher operates the courseware to demonstrate that the mooncakes are divided into 8 portions on average.

Teacher: We just divided a piece of moon cake into two, four and eight portions on average. If you had to choose one, which one would you choose?

Why? Ouyang Xiaolian, can you tell me?

Health: I will choose this one because it is bigger.

Teacher: But the following fractions, their denominators are all 4 and 8, both greater than 2? Why did you choose this?

Health: Because the more copies, the smaller each.

Teacher: What a wonderful speech! The applause encouraged her. (Organize students to tell Ouyang Xiaolian again. )

Teacher: The more copies, the bigger the denominator, and the smaller each copy.

The teacher guides the students to sum up and write it on the blackboard: the bigger the denominator, the smaller the score. )

Teacher: (The teacher organizes real-time exercises) Here are some pictures. Will you color them according to the score and judge the size?

(Practice and report in groups) Insert pictures.

○ ○

Teacher: (Call the roll to report the learning situation of the group. The key point is whether the students have mastered the method of comparing the scores of the same molecule. )

Health:.

Teacher: What knowledge is your judgment based on?

Health: My basis is: the greater the denominator of the same molecule, the smaller the score.

Teacher: That's great. Applause.

3, teaching 92 pages example 2:

Teacher: Take out your square paper and divide it into four parts equally. Let's see how different you are.

(Group cooperative learning)

Teacher: Mr. Zhong, would you please show the students your method?

Health: If I fold the square twice, I can divide it into four parts on average.

Teacher: You are so clever. Have other students thought of other different methods?

Health: I fold the square diagonally twice, or I can divide the square into four parts equally.

Teacher: You speak very well! Applause and encourage. For the "average score", as long as you use your head, you will find differences.

Third, consolidate new knowledge:

1, complete 93 pages of the book "Do it".

2. Finish pages 96 # 1, #2, #3 and #4 of this book.

Fourth, class summary: (name 3 ~ 5 students and talk about the gains of this class)

Verb (abbreviation of verb) Homework: study instruction (50 ~ 5 1)