First, pave the way.

1. Review (1), (2) Questions are presented by projection, (3) Questions are presented on the blackboard)

(1)4 is a fraction of 5? How many times is 5 than 4?

(2) Steel pipe length 12m, cut off 8m. A fraction of the total length is cut off.

(3) Grade five students 160, 120 meet the national physical training standards (children's group), accounting for a fraction of the number of grade five students. (1 person performance)

When revising, ask: Who is better than who? Who is this unit "1"?

2. Reveal the theme:

Students have mastered the solution of fractional application problems. On this basis, we learn the solution of the general application problem of percentage.

Writing on the blackboard: the general application of percentage

Second, explore new knowledge.

1. Teaching examples 1

(1) Change the "score" in the review question to "percentage" to become an example 1: There are 160 students in grade five, and 120 students have reached the National Physical Training Standard (children's group), accounting for a few percent of grade five students.

(2) Teachers inspire:

Example 1 compared with the review questions, the relationship between known conditions and numbers has not changed, but the relationship between two numbers has changed from a few fractions to a few percent. Think about it, class. Have the ideas and methods for solving these two problems changed? (No) In other words, the solution of the percentage application problem is the same as that of the fraction application problem. Then we solve the example 1 with the ideas and methods of solving fractional application problems.

(3) ask questions:

According to this question, think about it: who is better than who? Who is this unit "1"? How to calculate according to the solution that one number is a fraction of another number?

② What should the calculation result be?

(4) Let the students talk about the problem-solving process, and the teacher writes down on the blackboard:

120÷ 160=0.75=75%

A: It accounts for 75% of the sixth grade students.

(5) Teacher's summary: Finding a number is several times that of another number, and the quantitative relationship between score and percentage is the same, so the method of solving the problem is the same, but the expression of the calculation result is different.

2. Feedback exercise (projection demonstration)

Class One planted 40 trees and Class Two planted 48 trees. What percentage of trees have Class Two planted? What percentage of trees were planted in Class One, Class Two? (1 person doing it on film)

When revising, ask: Who is better than who? Who is this unit "1"?

3. Teaching Example 2

(1) shows the preparation question:

In a county seed extension station, 300 seeds were used for germination test, and 288 seeds germinated. What is the percentage of germinated seeds in the total number of experimental seeds?

Students do problems and show them by projection:

288÷33=0.96=96%

A: The number of germinated seeds accounts for 96% of the total number of tested seeds.

(2) We call the percentage of germinated seeds to the total number of tested seeds as germination rate.

Who can say what is the germination rate?

Teacher's explanation: before planting, seed germination test should be carried out, and the sowing amount per unit area should be determined according to the germination rate. This can not only ensure that the number of seedlings needed is not too much, but also avoid the waste of seeds. Therefore, seeking germination rate plays an important role in the bumper harvest of agricultural production. We must learn this part of knowledge well.

(3) Question: What is the actual germination rate?

Guide the students to find out: Why should we multiply 100% in the formula?

Because the germination rate is a percentage, the formula itself should be expressed as a percentage.

(4) Change the original question "What percentage of germinated seeds accounts for the number of experimental seeds" to "Seeking germination rate" as Example 2.

Please calculate the germination rate according to the formula. Question: What does the germination rate of 96% mean? (The number of germinated seeds accounts for 96% of the total number of tested seeds)

(5) Calculation of other percentages

① When students read a book, besides removing the germination rate, there are many calculated percentages. And read the relevant formulas.

(2) The teacher tells other examples of calculating percentage and asks students to tell the calculation formula.

Such as: oil yield, rice yield, passing rate and enrollment rate. ...

(6) do it.

(7) Summary: Calculate the percentage of germination rate and oil yield. As long as you understand the meaning of percentage and use the formula correctly, you can calculate it accurately.

Third, classroom exercises:

1, Exercise 9, Question 1

Question: Who is the unit "1"? The number before the percent sign is required to be an integer. How many decimal places should be taken as the approximate value of the quotient? How many decimal places should quotient be calculated?

The teacher stressed: pay attention to using approximate symbols when answering a sentence, and don't lose the word "about".

2. Exercise 9, Question 2 (directly in the book)

Revised question: The number of seeds tested is 300. Is there any change in germination rate of each test? In what range does it change?

Fourth, the class summary:

In this lesson, we learned to find an application problem, where one number is a few percent of the other. The idea and method of solving problems are basically the same as those of fractional application problems, but the results are converted into percentages. When doing the problem, we must accurately judge who the unit "1" is, which is the key to doing the problem. At the same time, we should master the formula of finding the correlation percentage and answer the question of finding the correlation percentage.

V. Creative work:

Go home and do a seed germination test to calculate the teething rate of seeds.

Teaching reflection:

Teaching theory holds that students' intelligence can only be brought into play when they experience or experience a learning process, and any learning is a process of active construction. There is a saying: "I heard it and forgot it; I saw it and remembered it; Experienced, I understand. " It can be seen that the best way for students to learn mathematics is to let them feel mathematics, experience mathematics and experience mathematics.

The learning of this lesson is based on students' learning "How many times is a number" and "How to find the quotient with the multiplication formula of 7, 8 and 9". Students have a certain knowledge base. This lesson focuses on students' practical operation and independent inquiry. By speaking, posing, drawing and designing independently, students can experience the whole process of transforming the practical problem of "how many times is one number another" into the mathematical problem of "how many other numbers does a number have". By solving problems, students learn to use the concepts they have learned and make simple analysis and reasoning. On the other hand, they can understand the quantitative relationship between many things around them and feel the application value of mathematical knowledge. In teaching, these aspects are outstanding:

1, with large capacity but clear organization.

In this class, I have to complete two examples and some exercises, and the classroom capacity is very large. I try to be clear in teaching design.

First of all, from the review of division and oral calculation, through games and hands-on operations, starting from the students' existing knowledge reserves, lay a good foundation for learning the problem that one number is several times that of another, so that students can initially feel "who is several times that of who". Then through the in-depth introduction of the game, the teaching of examples is introduced, so that students can participate in the whole process of transforming the practical problem of "how many times is one number another" into the mathematical problem of "how many other numbers does a number contain". After two examples, consolidate the new knowledge through a group of synchronous exercises. Finally, through the study of a group of open questions, students' thinking can be expanded and improved.

2, hands-on operation, enough time.

In class, I pay more attention to students' practical operation. From the introduction of review, I let students fully activate their knowledge reserves through activities such as posing and speaking. In the explanation of examples, I asked everyone to pose and speak, fully mobilized students' hands, brains and mouths, and organically combined operation with concept understanding. Not only that, but also the content of drawing and speaking is chosen in the design of the exercise questions, so that students can think first, then draw a picture by themselves and deepen their knowledge on the basis of operation.

3. Practice, the gradient is obvious.

The exercises designed by the teachers in this class have followed the principle of "from the shallow to the deep" and "combining support with release" since the introduction of review. First of all, I listened and calculated, reviewed "using the multiplication formula of 7, 8 and 9 to find the quotient", explained the meaning of division with 27÷9, and learned "who is several times who". At the same time, the same type of exercises are designed. After the example exercises, design a group of three basic questions, students can freely choose one of them to complete, and then communicate with each other in groups, which not only achieves the goal of consolidating the exercises, but also exposes each group of students to more questions in a relatively short time. The design of expanding exercise is a deepening exercise of the content of this course, which requires students to solve the problem of "how many times one number is another" according to the given information. Then there is an open question. Let students paint the original picture with two colors, find out the quantitative relationship between them, put forward different mathematical problems, and achieve the purpose of developing their abilities, so that students can consolidate new knowledge and gradually improve their abilities.

Mathematics curriculum standards point out that meaningful mathematics learning activities can't rely solely on imitation and memory, and hands-on practice, independent exploration and cooperative communication are important ways for students to learn mathematics. In the design of this lesson, I take students' hands-on operation as the main line, supplemented by students' autonomous learning and group cooperation and communication, so that students can actively participate in the whole process of transforming the practical problem of "how many times is one number another" into the mathematical problem of "one number includes several other numbers", and effectively understand it, so as to master new knowledge.