Let's start with teaching material analysis.
The parity of numbers is page 14- 15 of the first volume of the fifth grade of primary school mathematics published by Beijing Normal University. The "parity of numbers" is based on the fact that students have learned odd and even numbers.
Several different mathematical activities and games are arranged in the textbook, so that students can understand the law of odd-even changes of numbers, which can arouse students' thinking in the activities of exploring the law and help them find solutions to problems, thus using these methods to solve practical problems in life.
According to my understanding of the textbook, this lesson mainly designs two activities:
Activity 1: Let students understand the parity law of numbers through specific situations, and use the parity law of numbers to solve some simple practical problems. The main purpose is to let students discover the law that the ship starts from the south bank, "odd times on the north bank, even times on the south bank". (I changed the textbook to the law of students' flipping hands) to guide students in solving problems such as listing and drawing.
Activity 2: mainly use the above parity law to explore the parity change law in mathematical calculation. By trying the process of formula calculation-preliminary conclusion-example verification-conclusion, the law of adding odd and even numbers is explored to improve students' reasoning ability.
Second, talk about student analysis.
Grade five students have some methods to explore mathematical problems and experience in summing up laws, and their thinking is more active. They can find and ask math questions at any time. In the process of solving problems, we can choose effective solutions and strategies according to specific problems, sum up our own methods in time, and accumulate experience in application. Their curiosity and desire to explore are extremely strong, and they are eager to find the law. Through the front, I found that one third of my classmates have mastered what they have learned. Through the following teaching, I can let most students master what they have learned in this class, form an understanding and achieve their learning goals.
Third, talk about learning objectives.
1. Try to find the rules by "list" and "sketch", and solve some simple problems in life by using the parity of numbers.
2. Experience the process of exploring the change of parity. In addition, you can find the change law of parity in calculation in activities, experience research methods in activities, and improve your reasoning ability.
3. In the activity of learning "parity of numbers", students can be organized to actively participate in mathematics learning activities.
Teaching emphasis: discover the changing law of parity of numbers in addition and subtraction.
Teaching difficulty: Being able to explain some simple problems in life by using parity analysis of numbers.
Fourth, talk about the teaching process:
First, create a situation to stimulate students' curiosity
Do students like playing games? (Like), the teacher will play a game with you-flip hands. Have you ever played? In fact, there is a lot of math knowledge in the flip. Have you paid attention to it? Today, the teacher will see who observes carefully and get the mathematical law in palm flip. Do you have confidence?
Second, explore new knowledge.
(A) let students feel the equality in life
Activity 1: Teacher-student interaction, organize students to discover laws through various methods (flip hands).
1, let all students play games (flip hands)
The courseware shows the rules of the game: all students palm down, then palm up or down in turn, palm down again, and so on.
2. Think about whether the palm is down or up after five flips.
Student exchange: What do you think?
3. Do you want to solve the problem of palm down or up after flipping 100 times? What should I do? 1000 times and 9999 times?
(1) think independently
(2) Collective reporting and communication
(3) The teacher gives guidance on solving problems: list or drawing.
4. What do you find by solving these problems and observing the blackboard?
Flip odd times, palms facing each other.
After a few somersaults, palms facing each other.
5. Apply what you have learned: flip 100 times, 1000 times, 9999 times, palm up or down?
6 thinking: as long as the positions of the previous times are determined, all the positions of odd times can be determined? You can also locate all even times?
7. Thinking: Some people say that after the palm is turned 999 times, the palm is down. Is this correct? Why?
8. Ask at the same table: After the palm turns () times, the palm points to (). Why?
Activity 2: Expand and consolidate what you have learned.
1, so parity can help us solve some problems.
(1) Please try the cup in your hand on page 14 (courseware shows: put a cup on the table with its mouth up, flip it 1 time, and flip it with its mouth up twice. Turn 10 times, and turn 19 times, and the cup mouth will face. Try to explain why)
A, think independently
B, collective communication, say your own thoughts.
(2) Understand the relativity between odd and even numbers
Change the initial state of the cup, with the cup mouth facing down, to see if there is any regularity.
Question: Why did the odd cup face down just now, and now the odd cup really faces up?
Summary: Because the starting point is different every time. Therefore, the odd positions will also change. But as long as we remember the first position, we can change it.
2, combined with the actual life, use the knowledge to solve problems.
According to your life experience, can you give an example similar to what you learned today?
Independent discussion on the role of parity in calculation
1, show the following numbers and let the students judge what the numbers in the circle and box are.
1、 1 1、2 1、49、2 1、25、37、3、 10 1、87
2、 12、 18、20、6、34、80、 16、52
Even odd number
2. Explore the parity law:
(1) If you add and subtract any two numbers on a circle, I can tell whether their sum or difference is odd or even. (Believe it or not)
Want to know the secret that the teacher told so quickly?
(2) Ask students to add or subtract any two numbers in a square to see what rules you can find.
(3) Write several groups of addition and subtraction formulas of two even numbers for verification.
(4) Draw a conclusion: When both numbers are even, the result after addition and subtraction must be even.
(5) If two numbers are selected from a circle, is their sum or difference odd or even? Try to verify and draw a conclusion.
When both numbers are even, the result after addition and subtraction must be even.
(6) What should I do if I want to turn the sum or difference of two numbers into an odd number?
Some students may say: I want to choose a number from the circle and a number from the square. Their total number is odd.
Let the students try to verify and come to the conclusion that when two numbers are even and odd, the result after addition and subtraction must be odd.
3. Summary: What laws have you found through the research just now? Can you summarize it in one sentence?
(1), for two definite numbers, the parity after operation is the same regardless of addition or subtraction.
(2) When the parity of two numbers is the same, the result after addition and subtraction must be even; When the parity of two numbers is different, the result after addition and subtraction must be odd.
4. Test you: Complete question (7) on page 15 of the math book: Judge whether the result of the following formula is odd or even.
10389+20xx 1 1387+ 13 1 268+ 1024
287- 163 357- 168 1024-268 1024-267
Thinking: How do you judge?
Do you dare to challenge?
2+4+6+8+ 10……+998+ 1000
2+4+6+8+ 10……+998+ 1000+ 1
The students are doing well. By mastering these laws, we can discover some little secrets in life.
Third, practical application to solve problems.
1, personal collection
Can you find the question about the parity of numbers from the math books we read every day?
A. think independently.
B, collective communication.
Open and closed volumes correspond to the number of turns; Odd pages are on the front and even pages are on the back. ...
2, the secret of the switch
One night, when Naughty was doing his homework at home, the power went out. (This switch is turned on and off) Naughtily pressed the switch 12 times. Was the light on or off when the call came in? What happens when you press the switch 20 1 time?
(1) Think independently and discuss at the same table.
(2) Collective communication.
Fourth, talk about the harvest.
What have you learned?
Verb (abbreviation for verb) the arrangement of actual work
Judge the parity of the result and tell me what you find.
207- 13
207- 13- 1 1
207- 13- 1 1-43
207- 13- 1 1-43-25
207- 13- 1 1-43-25-49
Blackboard design:
List drawing method
exceed
Five, say after-class reflection
My feeling is:
1, the purpose of creating problem situations is to create an atmosphere for students to explore in class, thus stimulating students' interest in learning, providing students with opportunities for self-expression and cultivating students' awareness of problems. According to the characteristics that students are more interested in games. I designed the game of handspring. Judging from the classroom effect, the students are very interested and eager to try. But after turning over 100 times, the students tried dozens of times and then stopped. Students' learning mood is rising gradually, and they are eager to find the law. At this time, the teacher seized the opportunity of students' curiosity and asked, "What laws have you found?" Question, this question introduces students to explore questions in a timely manner.
2. Pay attention to students' activities, guide students to solve the addition and subtraction of odd and even numbers with the learning method of "trial formula-drawing preliminary conclusions-verifying with examples-drawing conclusions", and improve students' reasoning ability.
In this class, there are only two activities and two "try it" in the textbook, and there are almost no exercises. The exploration process of the two activities is also very simple, and students can get the correct answer with a little thinking. Before class, I consulted some materials, further expanded the "flip cup game" and "exploring the parity of integer addition and subtraction", and added some exercises to enrich the content, but the typicality and hierarchy of the exercises are not enough and need to be improved.
4. The example of parity of numbers is somewhat inappropriate. I should use the resources generated in class to practice flexibly.
5. The blackboard writing in math class must be able to explain the key points and clarify the difficulties. My blackboard writing is too simple.
6. I can influence students' attitudes with my own emotions in emotional contagion and my attitude, so that students can think while having fun, complete the teaching tasks in an all-round way and achieve the teaching objectives.
7, timely evaluation of students, so that students feel the joy of success.
Reflecting on this lesson, I think we should examine our own teaching in time, adjust students' emotions and guide students to actively participate in the classroom. In the design of exercises, we can use the resources generated in the classroom to practice flexibly, rather than rigidly, which requires teachers to correctly handle the preset and generated resources. We should also improve our adaptability, deal with random situations in the classroom and strengthen the timely, accurate and appropriate evaluation of students.