Knowledge and skill goal: understand the percentage in life, master the method of calculating percentage, and calculate percentage correctly. Process and Method Objective: To understand the meaning and calculation method of commonly used percentage through independent inquiry and cooperative communication. The goal of emotion, attitude and values: to know the usefulness and necessity of seeking percentage, to feel that percentage comes from life, and to infiltrate the mathematical thought that mathematics comes from life and serves life.

Emphasis and difficulty in teaching

Teaching emphasis: understand the meaning of common percentages in life.

Teaching difficulty: correctly calculate the commonly used percentage.

teaching process

First, create a situation, explore the import

1, courseware demonstration

Look at the picture and answer the following questions.

(1) What percentage of the whole graph does the shadow occupy? How to express it in percentage?

(2) What is the proportion of the blank part in the picture to the shadow part? How to express it in percentage?

2, the meaning of percentage

36% of the students in our class joined the art interest group.

About 50% of the world's population is under the age of 25.

The fruit juice content of a bottle of fruit grower's drink is about 10%.

The myopia rate of students in our class is 45%.

3. Xiaogang did 10 and made two mistakes.

What percentage of the total number of questions did you answer correctly?

What percentage of the total number of questions is wrong?

What percentage of all the questions did you answer correctly?

What percentage of the total number of questions is wrong?

What percentage of A is B, and what percentage of B is A? The method is the same: a? b

4. In the sixth grade, there are 160 people, and 120 people meet the national physical exercise standards (children's group), accounting for a fraction of the sixth grade? Grade six students 160, 120 meet the national physical training standards (children's group), which percentage of grade six students?

Students think independently and communicate at the same table: try to calculate and draw a conclusion.

5. Talk about and introduce new lessons.

In our daily life, there are many percentages like this, such as germination rate, pass rate and rice yield, which can help us solve some practical problems in life.

Next, let's go into percentage and explore its calculation method (blackboard writing: calculation of percentage).

Second, learn new knowledge.

1, teaching example 1 Understand the percentage in a specific situation and explore the calculation method.

(1) Example 1: Sixth grade students 160, 120 meet the national physical exercise standards (children's group). What is the success rate of sixth grade students?

(2) Students read the question, analyze the meaning of the question, think about the meaning of the success rate, and try to calculate.

(3) Call the blackboard to exchange ideas and correct them collectively.

(4) Teacher's summary

Guide students to make it clear that the compliance rate is a percentage, what does it mean? What percentage of the total number of people who meet the standards are tested? , what else? What fraction of one number is another? The calculation method of the problem is the same, so use? How many people meet the standard? Test the total number of people? Just do it; Because percentage is a percentage, the calculation result should be in the form of percentage, so the complete calculation method should be? Compliance rate = the number of people who meet the standards divided by the total number of people tested? 100%? .

Talk: According to the National Standards for Students' Physical Health, the primary school students' physical health compliance rate is not less than 60%. Through calculation and comparison, it shows that the physical quality of students in our class has reached the health standard, which is also a percentage value.

2. Teaching Example 2 Master the calculation method of percentage and realize the value of percentage.

(1) Example 2: In the science class, the results of the seed germination experiment made by the students in Class 5 (2) are as follows:

Seed name: the total number of seeds in the experiment and the germination rate.

Mung bean 80 78

Peanut 50 46

Garlic 20 19

(2) Students read the questions, find out the known conditions and problems, discuss the significance of germination rate, and try to calculate the germination rate of various seeds. (3) Tell the meaning and calculation method of student exchange germination rate, board formula and collective correction.

(4) Understand the value of germination rate in production practice.

Through calculation, we find which seed has higher germination rate? Which is lower? Description: Germination rate is very important for farmers to farm. They need to decide the seed variety and planting area according to the germination rate.

3. Explore in groups, find out the percentage in life and summarize the percentage calculation formula.

(1) Talk about defining the requirements of cooperative learning: In real life, there are still many percentages such as hit rate, success rate and germination rate. Ask four students in the group to use their brains and cooperate actively to find out the percentage in life and write its calculation method, and compare which group finds the most.

(2) Group cooperation, find out the percentage in life, explore its significance and calculation method, write the calculation formula, and teachers patrol to understand the situation and results of group cooperation.

(3) The group representative reports the percentage collected by the group, clarifies its meaning, and displays the calculation method on the projector, which is modified by teachers and students.

(4) enumerate the calculation methods of different percentages, guide students to find the same points, and summarize the calculation formula of percentages. Rate = quantity? Divided by the total quantity? 100%

(5) Take examples to deepen the understanding of the percentage calculation formula and master the percentage calculation method.

4. In a county seed extension station, 300 corn seeds were used for germination test, and 288 seeds germinated. Find the germination rate.

5. Discuss and communicate: What percentage in life may be greater than 100%? What will only be equal to or less than 100%? Third, consolidate the practice.

1, fill in.

(1) The rice yield is 85%, which means ()

100% of () kg.

Eighty-five percent

② A number is 4/5 of B number, and B number is A number.

( )%。

③20? ( )= 4/8 =( )︰24=( )%

2. Choose one:

A number of trees were planted, and 100 trees were alive and 1 tree was dead. The correct formula for finding the survival rate is ().

A steel pipe is cut into two sections, the first section is meters long and the second section accounts for 60% of the total length. These two steel pipes are opposite (). arrange work

1, group cooperation, sorting out the calculation method of common percentages in life, written on page 86 of the math book.

2. Complete questions 2, 3 and 4 in Exercise 20.

Fourth, class summary.

What did you buy today? Life is about harvest.

The teacher summed it up.

Solving teaching plans with percentages (2) Teaching objectives

1, so that students can deepen their understanding of percentages and understand the meaning of these percentages, such as germination rate, flour yield and qualified rate.

2. We can solve the application problem of how many percent of a number is another number by finding out how many percent of a number is another number, and solve some simple practical problems in life.

3. Cultivate students' knowledge transfer ability and mathematics application consciousness.

Emphasis and difficulty in teaching

Solve the application problem that one number is a percentage of another number.

teaching tool

courseware

teaching process

First, review the old knowledge:

1. Last year, a township planned to afforest 12 hectares and actually afforested 14 hectares. What percentage of the original plan was actually afforested?

Name the students to answer.

2. Last year, a township was originally planned to afforest 12 hectares, but actually afforested 14 hectares. What percentage of actual afforestation has increased compared with the original plan?

Name the students to answer.

Second, cooperate with each other to explore problems:

(a) Preliminary views

1, students try to answer the questions themselves? What percentage of all the questions did you answer correctly? And then what? What percentage of the total number of questions is wrong? problem

2. summary:? Find the percentage of one number to another. With what? How to find the score of one number to another? The solution is the same, the key is to find the right unit? 1? The difference is, Find the percentage of one number to another. The calculation result should be converted into percentage.

(2) * * * with discussion

1, the percentile system is widely used in daily life and work. As mentioned above, in the oral arithmetic competition, what do you have respectively? What percentage of all the questions did you answer correctly? This is your correct rate in this oral arithmetic contest. What percentage of the total number of questions is wrong? It is the error rate. What do we usually call these correct rates and error rates? Percentage? Can you give some examples of percentage in our daily life?

2. Students give some examples of percentages in daily life, and at the same time ask students to talk about the significance of the percentages he quoted.

The percentage quoted by students on the blackboard and its meaning. For example:

3. Try to solve the example:

(1) Conditions for displaying textbook example 1( 1):

Example: 1: Grade 6 students 160, 120 meet the national physical exercise standards.

(2) Students ask questions and try to answer them.

(3) Students independently complete the example 1(2)

Third, use knowledge to solve problems:

1，P86？ Do it. Question 1 and 2

2. Exercise 20, Question 2

Fourth, the class summary

1, students talk about what you have gained after learning this lesson. What is the key to solving the application problem that one number is the percentage of another number? What is the method? What is the relationship between this kind of application problem and finding a fractional application problem in which one number is a fraction of another number?

What is the use of what students have learned today in our daily life?

Classroom summary

Students talk about the key to solving the application problem of calculating the percentage of one number to another.

Verb (short for verb) Homework:

Exercise 20, questions 3 and 4.

homework

Exercise 20, questions 3 and 4.