Beijing Normal University Edition Nine-year Compulsory Education Primary School Mathematics Grade Five Volume Two Fractions Mixed Operation (1).

Textbook description

"Fractional mixed operation (I)" is a new content after learning the contents of fractional mixed operation in the first volume of grade five and fractional multiplication and division in the third unit of this volume. In daily life, we often come into contact with some problems that need to be solved by score calculation. The textbook follows the characteristics of this set of textbooks when arranging fractional mixed operation, and leads to fractional mixed operation in solving practical problems, thus making students realize the necessity of operation, and laying a foundation for learning the operation law of fractional multiplication and answering the questions of fractional mixed operation in the future.

Teaching objectives

1, the operation order of fractional mixing operation is the same as integer, and fractional mixing operation will be calculated (mainly in two steps, no more than three steps).

2. Use fractions to add, subtract, multiply and divide to solve practical problems in daily life and cultivate application consciousness.

3. Develop language skills and educate on environmental protection and water saving.

The focus of teaching is to correctly calculate the mixed operation of fractions.

Teaching difficulties: using fractions to add, subtract, multiply and divide to solve practical problems in daily life.

Prepare courseware before class

teaching process

First, use old knowledge to introduce new lessons.

Teacher: Yesterday, I heard that all the students in our class are experts in verbal arithmetic. I'm going to test you today to see if it's really what I heard. Do you have confidence?

(Showing courseware: I am an expert in oral arithmetic)

Teacher: The students are really amazing. As I have heard, I admire you very much! The teacher heard that you are not only good at verbal arithmetic, but also good at mixed arithmetic. I can't wait to know your knowledge of mixed operation. Please see: (Courseware: Who comes first in mixed operation)

Teacher: It's really amazing! Since everyone is so proficient in integer mixed operation, in the next study of fractional mixed operation, the teacher believes that you must not be outdone, so master it quickly. Let's walk into today's mathematical world and study fractional mixing operation together. (blackboard writing topic)

(Design intention: Teachers stimulate students' interest in learning through encouraging language, so that students can devote themselves to learning new knowledge with full enthusiasm.)

Second, create situations and explore new knowledge.

1, create a situation and lead to new knowledge:

Teacher: Spring is a vibrant season. Look, the students from the school interest group also came to the spring field together. (Courseware Demonstration: Question Situation)

Teacher: What mathematical information do you find from the picture? Can you ask suitable math questions based on this information?

Solve the problem: How many people are there in the model airplane team?

2. Independent investigation

Teacher: Can you use a line graph to represent the quantitative relationship in the question? what do you think?

3. Cooperation and communication

Teacher: Talk about your ideas in the group. Who can share their ideas with the class? Let students analyze and solve problems, and teachers should guide them appropriately.

(Design intention: Give students the initiative in learning and fully mobilize their enthusiasm and initiative in learning. Teachers combine students' existing knowledge structure and life experience, and boldly throw the space for learning and exploration in class to students, so that students can get the opportunity to display their individuality. Teachers' inspiring evaluation language makes children feel success and joy. )

4, column calculation, master the algorithm.

Ask the student representatives to write their own formulas on the blackboard.

Number of photography teams: 12× 1/3=4 (people). Please continue to use the comprehensive formula:

Number of model airplane teams: 4×3/4=3 (people) 12× 1/3×3/4.

=4×3/4

=3 (person)

Teacher: Is there any different algorithm for this problem?

How much does the model airplane team occupy in the meteorological team: 1/3×3/4= 1/4.

Number of model airplane team: 12× 1/4=3 people.

Comprehensive formula: 12×( 1/3×3/4)

= 12× 1/4

=3 (person)

Teacher: Look at two comprehensive formulas. What is their operation sequence?

Conclusion: The operation order of decimal multiplication and integer multiplication is the same.

Teacher: It seems that the mixed operation of fractions is related to the mixed operation of integers. Can it be popularized?

Teacher: In the fractional mixing formula, if there is only addition and subtraction or only multiplication and division, what order should it be calculated?

Teacher: What about addition, subtraction, multiplication and division?

Teacher: In the mixed operation of fractional multiplication, if you can cut the point, you can cut the point first and then calculate.

Guide students to draw the conclusion that the order of fractional mixing operation is the same as that of integer mixing operation.

(Design intention: Teachers put themselves in the position of organizers, guides and collaborators of students' learning activities, so as to create a relaxed, democratic and harmonious learning atmosphere for students, and let each student participate in independent exploration and cooperative exchange of learning activities. )

Third, feedback exercises.

Teacher: Through the intense and orderly study just now, the students already know that the order of fractional mixing operation is the same as that of integer mixing operation. How do students master it? It's time to verify it. Don't you want to check it yourself?

1, say the operation sequence first, and then calculate. (Courseware demonstration)

In groups, four students perform on the blackboard.

2. Solve mathematical problems in life.

There are about 660 cities in China, of which about two thirds are short of water. Among these cities with insufficient water supply, about14 cities are seriously short of water. How many cities in China are seriously short of water?

(Design intention: To infiltrate water-saving education for students by solving practical problems in life. )

3. Math Story: (Courseware)

Teacher: Can you tell us the meaning of this story in your own language?

Analyze the meaning of the problem and solve it.

Fourth, self-summary.

Teacher: It will be over in 40 minutes. Today, we learned new knowledge about fractional mixed operation in the mathematics kingdom. Can you tell us what new knowledge we have learned? What's your score in this class?

(Design intention: Let students learn to sum up and reflect on themselves, and make continuous progress in reflection)