1, through the familiar life scenes of students, put forward the problem of addition and subtraction, explore the whole addition and subtraction, and go through the process of oral calculation.
2. Solve practical problems in life by exploring calculation methods by yourself. Enable students to do oral calculation correctly and skillfully and improve their oral calculation ability.
3. Cultivate students' good habits of careful examination of questions and careful oral calculation. Teaching emphasis: master the method of adding and subtracting whole hundred and whole thousand digits.
Teaching difficulties:
Correct addition and subtraction of whole hundred and whole thousand.
Teaching preparation: courseware
Teaching process:
First, review before class:
1, fill in the blanks:
(1)80 has () tens in it.
(2) 700 has () 100.
(3)3000 has () thousand. There are () hundreds in 3000.
(4)3756=( )+( )+( )+( )
2. Composition of numbers:
The number of (1) 4200 is ().
(2)5800 consists of () thousand and () hundred.
Second, the courseware appears:
1. Guide the students to observe carefully: What did Grandpa buy? Grandpa went to the mall to buy electrical appliances and bought a TV and a refrigerator.
2. Ask students to ask math questions according to the information in the picture. (talking to each other in the group)
3. Questions raised in the student report:
(1) How much did Grandpa spend?
(2) How much cheaper is the TV than the refrigerator?
(3) How much does it cost Grandpa to buy a refrigerator more than a TV?
Think about it: what methods should be used to solve these problems?
3. Today, let's discuss the addition and subtraction methods of integer hundred and integer thousand:
(emerging topic: addition and subtraction of integer hundred and integer thousand)
1. Please choose one or two questions and try it yourself.
If you have difficulties, you can communicate with your partner. ) Students finish the exercise 1.
2. Student report:
Default 1:
How much did grandpa spend? 1000+2000=3000 (yuan) A: Grandpa spent 3000 yuan.
The teacher asked: What do you think? Why use 2- 1 on thousands? Any other ideas?
Default 2:
How much is the TV cheaper than the refrigerator? 2000- 1000= 1000 (yuan) A: The price of TV is lower than that of refrigerator 1000 yuan.
The teacher asked: Can you say what you think? Who else has a different idea?
Default 3:
How much does it cost grandpa to buy a refrigerator more than a TV? 2000- 1000= 1000 (yuan) A: Grandpa spent more on a refrigerator than on a TV 1000 yuan.
The teacher asked: How can I ask this question? How much is the refrigerator more expensive than the TV? )
3. Let's practice now:
3000+6000= 3000+2000= 5000+300= 7000+200=
(Make use of the mistakes made by the students, demonstrate with a counter, and ask the students: Where should I dial the 200 beads? )
9700-5000 = 5000-4000 = 8000-3000 = 6000-1000 = (use courseware when modifying)
Grandpa has come to the kitchen appliance store now, and he is going to buy these things.
Courseware appears:
Electric kettle 80 yuan thermos bottle 50 yuan rice cooker1Grandpa 30 yuan asked his classmates to help him calculate:
(1) How much should an electric kettle and a thermos be given to the clerk?
(2) What is the difference between an electric kettle and a rice cooker?
Students solve two problems independently and then exchange ideas with their peers.
Student report:
80+50= 130 (yuan) A: To buy an electric kettle and a thermos bottle, you have to pay the salesman 130 yuan.
This is the teaching difficulty. Please demonstrate this with a stick to highlight arithmetic (decimal) and ask students to express their ideas. 130-80=? There is a difference between an electric kettle and a rice cooker in 50 yuan. )
The teacher asked: What do you think?
After the students answer, the teacher uses the counter to guide from the counting unit: 13 ten MINUS 80.
5. Appear: 900+600=? 1500-600=?
The teacher asked: What should I pay attention to when calculating? (The same counting unit can be added or subtracted; If the addition exceeds ten decimal places and the subtraction is not enough, the first digit is "1". )
Exercise: 4000+6000 = 3600-3000 = 3700+300 = 2000-600 =
6. Compare two examples and make a summary:
The former: directly calculated according to the counting unit, without carrying or giving way; The latter: calculation: when adding to ten decimal places, if the subtraction is not enough, the first digit is "1".
7. Practical application and consolidation exercises:
(1)P82 question 2 (2)P83 question 1
Fourth, the class summary:
What did you learn in this class?
The second teaching goal of the second volume of the second grade mathematics is "integer hundred, integer thousand addition and subtraction";
1, let students find problems in the scene, explore the addition and subtraction methods of integer hundred and integer thousand in the process of solving problems, and choose their favorite method to calculate correctly among various methods.
2. Cultivate students' ability of independent thinking, cooperation and communication to solve simple practical problems.
3. Experience the close relationship between mathematics and life, and form good thinking habits.
4. Cultivate students' self-confidence in communication and evaluation.
Teaching focus:
Master the calculation method of addition and subtraction of whole hundred and whole thousand.
Teaching difficulties:
Master oral arithmetic and dictate its reasoning.
Teaching process:
First, create situations and ask questions.
Create a TV and refrigerator and ask questions you want to know (unit price, total, difference).
Second, Lenovo guesses and clarifies the direction.
1. Organize unit price guessing activities.
2, clear exploration direction
Third, independent exploration and achievement display.
1, try independently, try first (complete two questions at the same time)
2. Teamwork, questioning and posing problems
3. Show the results and get the algorithm.
The first question: 1000+2000=3000 yuan.
1) Number: 1 thousand plus 2 thousand is 3 thousand, and 3 thousand is 3,000.
2) See the big from the small: take out 1+2=3 1000+2000=3000.
3) Remove three zeros from two addends, then add them, and then add three zeros at the end of the addend.
4) 1+2=3, 10+20=? , 100+200=? , 1000+2000=3000, 1000+500=? To analyze and demonstrate that the number of zeros should be the same)
Second question: 2000- 1000= 1000 (meta) method is the same as above.
4. Transfer analogy and improve the algorithm (e.g. 10 variation)-"add and get the difference" method.
Dad spent 3000 yuan on a TV set and a refrigerator. It is understood that the unit price of this TV set is 65,438+0,000 yuan. What is the unit price of the refrigerator?
5. Use new knowledge to solve problems (such as 10 and the topic of doing something)
Teacher: It's amazing. Everyone not only helped the little head father get the money right, but also came up with so many good ways to solve the problem in the process of calculating the money. They opened the book and finished two questions: P8 1 case 10 and Congcong, a clever elf.
1, for example 10: 80+50 = 130-80 = (say ideas)
2,900+600 = (from Yi Xianger: 1500-600 = 900, 1500-600 = 900)
(Presentation topic: Addition and subtraction of integer hundred and integer thousand)
Fourth, simulation exercises, expanding applications
1, the truth is right and the red color is reasonable.
70+50= 800+400= 3000+6000=
9000-5000= 1200-500= 1500+ 1000=
2. The first question of mouse game P84. Let the students finish independently first, then ask each other questions at the same table, then ask the whole class for help and organize students' comments. )
3. Expansion problem. Fill in whole hundreds and thousands in ().
( )+( )=700 1000-( )=( )
4. Little daddy has money. * * * brought 5000 yuan. Is it enough? How much is left?
Fifth, summarize and improve cognition.
1. Students report what they have learned.
2. Teachers assess the learning situation.
The third teaching goal of the second volume of the second grade mathematics "Integer Hundred, Integer Thousand Addition and Subtraction";
1. Let the students find problems in the scene, explore the addition and subtraction methods of integer hundred and integer thousand in the process of solving problems, and choose their favorite method to calculate correctly among various methods.
2. Cultivate students' ability of independent thinking, cooperation and communication to solve simple practical problems.
3. Experience the close relationship between mathematics and life, and form good thinking habits.
4. Cultivate students' self-confidence in communication and evaluation.
Teaching focus:
Master the calculation method of addition and subtraction of whole hundred and whole thousand.
Teaching difficulties:
Master oral arithmetic and dictate its reasoning.
Teaching aid: courseware
Teaching process:
First, the game import:
Students, the teacher knows that your favorite cartoons are Pleasant Goat and Big Big Wolf! Well, Pleasant Goat came to our class today. Are you welcome? Then extend your little hand to welcome you! Pleased to meet you, Pleased Goat. He wants to play games with his classmates. Would you like to? This game is called number synthesis. Pleasant goat says 4000, which is composed of 4000. Who will say it again? Then would you say this whole hundred and whole ten composition?
The students are very clever, and they will learn as soon as they learn. Having said that, we can calculate the addition and subtraction of whole thousand numbers by mouth according to the composition of numbers. In this lesson, we will learn the addition and subtraction of integer hundred and integer thousand. (blackboard title: addition and subtraction of integer hundred and integer thousand)
Second, communication and exploration.
Today, Pleasant Goat is moving to a new home. He wants to buy some household appliances. Do you want to see what it wants to buy? Pleasant goat came to the shopping mall. There are so many home appliances here! Let's see which household appliances Pleasant Goat has seen (display pictures: TV, washing machine, DVD, refrigerator). Pleasant goat has encountered a problem. The assistant aunt asked him to guess the price of the goods, and only bought it when he guessed it correctly. This one stumped Pleasant Goat. Are you willing to help him?
(1) Pleasant Goat said it would cost 900 yuan to buy a washing machine. How much is that? (Courseware shows 900 yuan)
(2) The price of TV is the smallest four digits. Who can guess how much this is? (1000 yuan)
(3) Pleasant Goat said that six DVDs cost 100 yuan. How much is that? (600 yuan)
(4) The refrigerator is the most expensive, which is equivalent to the price of two TV sets (2000 yuan).
The students are really smart. The prices of these goods are suitable. Pleasant goat wants to buy two pieces of household appliances. Please discuss in the group which two products do you suggest Pleasant Goat buy, and find out the answer. (group discussion)
3, each group of reports
I want him to buy a TV set and a refrigerator. He can watch TV when he is free, and the refrigerator can help him store all kinds of food.
It's very thoughtful of you to help him figure out how much it will cost to buy these two home appliances.
1000+2000=3000 yuan (blackboard writing)
Do you have to count this? How did you work it out? (1 thousand plus 2 thousand is 3 thousand, and 3 thousand is 3,000. (Who else does this? (Talking to three classmates) What shall we do with it? Shall we give this method a name? (Method of synthesizing numbers)
Are there any other algorithms? (1+2=3, so 1000+2000=3000), (chatting with three students)
Which of these two methods do you prefer?
Health 1: I like the second method because it is not easy to make mistakes.
Health 2: I like the second method because it is simple and can get the answer quickly.
Health 3: …
The students all like the second one, so we should choose this convenient and quick method to do the problems in the future.
(2) Which group will report?
(3) The students are really amazing. They gave Pleasant Goat a lot of ideas. Who is the most expensive of these four commodities? How about the cheapest one? Then can you help Pleasant Goat find out how different they are? (2000-600= 1400 yuan) How did you work it out? (20-6= 14, so 2000-600= 1400) What should I do if I use the digital synthesis method? (20-600 =1400, so 2000-600= 1400)
Then can you still answer the question of subtraction calculation like this?
3. Teacher: The students raised valuable questions. And they can all be solved, which is really admirable! Now, Pleasant Goat has its own ideas. He bought a TV set and a refrigerator and drove home happily. (showing pictures)
Pleasant Goat came out of the shopping mall and went home through the library. Can you help Pleasant Goat figure out how many kilometers he has to walk to get home? (80+50= 130 km) How did you work it out? (Eight tens plus five tens is 13 tens, which is 130. ) Are there any other algorithms? (8+5= 13, so 80+50= 130) Then can you list two subtraction formulas according to this addition formula? (130-50=80, 130-80=50) On what basis did you work out their figures? (According to the addition of 80+50= 130, you get two subtraction numbers) Oh! Want to add and subtract, teacher, and a set of numbers. Can you list two additions and two subtractions according to these three numbers? (900+600= 1500 600+900= 1500 1500-900=600 1500-600=900)
Third, consolidate the application
1, the students are really good. You have solved all these problems that Pleasant Goat gave students. Now can you calculate the addition and subtraction of whole thousand numbers? Then we should not only know how to add and subtract thousands, but also calculate accurately and quickly. Pleasant goat also wants to test you. Are you confident to accept the challenge?
? Let's look at the first level: show the courseware. There is a question behind every box. You have to look at the problem and say the numbers quickly. Whoever raises his hand first will be called by the teacher first!
Let's relax and play a game after the tense game. The teacher divided the students into four groups. The teacher has many problem cards. The first group of students stood up when the score was 1000, the second group stood up when the score was less than 1000, and the third group stood up when the score was greater than 1500. Did you listen to the request?
Fourth, summary.
It seems that all the students have mastered the whole thousand oral calculation methods. Look! Pleasant goat gives you a thumbs up. He must be saying that you are good children! Pleasant goat is going home. He hopes his classmates will work harder in their future studies. Can you do it? This class is over. Class is over.
Four teaching contents in the teaching plan of "addition and subtraction of integer hundred and integer thousand" in the second volume of second grade mathematics;
Compulsory Education Curriculum Standard Experimental Textbook Volume II Grade 2 8 1 Example 9 Page 82 Example 10, doing problems and exercises.
Teaching material analysis:
The content of this section plays an important role in understanding the number within 10 thousand, and lays the foundation for other disciplines and future study. Buy a new color TV and refrigerator for grandpa's family, so that students can find and solve math problems from the data provided by the situation map. How much is the textbook? This textbook does not describe and memorize the rules of addition and subtraction of integer hundred and integer thousand, but focuses on students' understanding and application of the calculation process and method of addition and subtraction of integer hundred and integer thousand.
Analysis of learning situation:
According to the actual situation of students in this class, the connection between this class and old knowledge, and the age characteristics of students, I actively adopt vivid and diverse teaching methods and students' extensive and active participation in learning methods, effectively allowing students to internalize the addition and subtraction of integers through analogical reasoning. After exploring the complete method of adding and subtracting hundreds of digits, students conduct comparative exercises to guide them to choose the appropriate method of oral calculation according to different topics. Experience the joy of success.
Teaching objectives:
1, let students put forward and solve mathematical problems in situations, and master the calculation method of "addition and subtraction of whole hundred and whole thousand" on the basis of understanding.
2. Let students experience the diversity of the "whole hundred plus and minus thousand" algorithm through independent thinking and group cooperation and communication, and choose the favorite method to calculate correctly, so as to cultivate students' preliminary mathematical communication ability and cooperation consciousness.
3. Let students ask questions, solve problems and feel that mathematics comes from life. Cultivate students' self-confidence in exchange evaluation and experience the joy of success.
Teaching emphasis: addition and subtraction of whole hundred and whole thousand.
Difficulties in teaching: mastering oral arithmetic and dictating its reasoning.
Teaching preparation: multimedia courseware
Teaching process:
First, stimulate the introduction of interest.
1, oral calculation
40+50= 90-60= 90+ 10=
80-50= 60+30= 100-70=
Step 2 fill it in
(1)80 contains () ten digits; There are () tens in 150.
(2) there are () hundreds in five hundred; 1300 has () hundreds.
3. Guess what is the number in the teacher's hand?
1200 3600 650 80
At the teacher's prompt, let the students guess the numbers above. And observe the characteristics of the above figures and talk about the composition of the figures.
Teacher: By using the law of number composition, we can add and subtract whole hundred and whole thousand numbers orally. (Presentation topic: Addition and subtraction of integer hundred and integer thousand)
Second, try independently and explore the algorithm.
1, create a situation. Teaching example 9
Teacher: During the May Day holiday, the shopping mall held promotional activities. Uncle Wang spent 1000 on a TV set and 2000 on a refrigerator.
2. What math questions can children ask when they see these two math information? Default value:
(1), how much is a TV set and a refrigerator?
(2) How much cheaper is a TV than a refrigerator?
(3) How much is the refrigerator more expensive than the TV?
The students raised such valuable questions. Can it be solved?
The students tried to solve the first problem.
1000+2000=
How to calculate 1000+2000? Independent calculation, deskmate communication algorithm, feedback (several possibilities are as follows:)
Health: 1 thousand plus 2,000 is 3,000, and 3,000 is 3,000.
Health: Take out 1+2=3 1000+2000=3000.
Health: Take out from 1000+2000=3000 100+200=300.
3, method optimization, (students really want to come up with so many methods, so many methods, which one do you like? )
4. Can you solve the other two problems?
(1), choose a topic formula to calculate.
(2) AC algorithm. Tell me what you think,
Three. Teaching examples 10
1, organize activities, compile questions, and do oral calculations
Show the numbers 50, 80, 130, work out an addition formula and a subtraction formula in pairs, and write the formulas in the exercise book.
2. Presentation: 80+50 = 130-50=
Student communication algorithm. (omitted)
Presentation: 80+50 = 130-50=
Student communication algorithm. (several possibilities):
Health 1: 8 ten plus 50 13 ten is 130.
Health 2: From 8+5= 13 to 80+50= 130.
Health 3: Calculate 8+5= 13 first, and add the following 0, which is 130.
130-50=80.
Health 1: 13 Ten minus fifty equals eighty. Eighty points is eighty.
Health 2: From 13-5=8 to 130-50=80.
Health: I thought of it by addition, 80+50= 130, 130-50=80. (Want to add and subtract)
Teacher: His ideas are different from others. What do you want to say to him?
Health: He's great!
Teacher: You are really something. You know addition and subtraction are good friends. The addition formula must have a corresponding subtraction formula. Using this law can provide convenience for our calculation.
Now, please look at the textbook. Finish them, and if you have any questions, please ask.
3. Open the book, P8 1 There are two questions for Cong Cong, the elf, to test you. Come and show your skills!
900+600= 1500-600=
Talk to each other at the same table about calculation methods
4, teachers and students * * * Summary: You can use different methods to calculate the addition and subtraction of whole hundred and whole thousand numbers, whichever method you think is the simplest.
Fourth, consolidate and expand.
1, write a book, do 1 topic.
Teacher: Let's compare and see who can calculate quickly and accurately. Please stand up when you are finished, and then check collectively. Please sit down if you are right, and tell me why you are wrong if you are wrong. Can you correct it yourself?
2. Several groups of good friends have appeared. Let's do a quick calculation.
670-600 670-60
4000+200 4000+2000
1800+2000 1800+200
700-500 700-50
Good students think: what should these good friends remind us to pay attention to when calculating? Remind us that the same numbers should be aligned when calculating. )
3. Catch a mouse game.
Teacher: There is so much grain in the granary, but it also attracts many mice. What should I do?
The students put forward the strategy of killing rats.
Teacher: Let's invite the cat to catch it. This is the most ecological method. Look, here they come:
Health: I am a flower cat, specializing in catching 900.
Health: I am a yellow cat, specializing in catching 1000.
Health: I am a black cat, and I specialize in catching 1500.
Teacher: Let's cheer for them and help them loudly at the same time. The game begins.
Health: Come on! Come on!
Health: Flower cat! You got the wrong guy!
Health: Black cat! One of yours was taken away by a yellow cat! Go get it back. ……
Verb (abbreviation for verb) class summary.
Teacher: What did you learn from this class?
Health: I learned to add and subtract whole hundred thousand numbers with my mouth.
Student: I know that learning mathematics requires careful observation, careful listening and careful thinking.
Health: I see. I should praise the merits of my classmates.
Teacher: In this class, everyone has proved that he is a clever boy through hard work. Please say proudly-I am the best!
Blackboard design:
Addition and subtraction of integers
(1), how much is a TV set and a refrigerator?
Refrigerator map TV map
(2) How much cheaper is a TV than a refrigerator?
(3) How much is the refrigerator more expensive than the TV?
1000+2000=3000
2000- 1000= 1000