Teaching design of four operations in the next semester of mathematics in the fourth grade of primary school P4/ Example 1, Example 2 (only mixed operations of the same grade operations)
Teaching objectives:
1. Make students further master the same operation sequence as the operation level.
2. Let students experience the process of exploring and communicating to solve practical problems, and feel some strategies and methods to solve problems.
3. In the process of solving practical problems, make students develop study habits such as careful examination of questions and independent thinking.
Teaching process:
First, the theme map introduction
Observe the picture and ask questions according to the conditions.
(1) What are the people doing in the picture? How many activity areas is the world of ice and snow divided into? How many people are there in each district? how do you know
Organize students to ask questions and answer simple questions directly.
(2) According to the information in the picture, what problems can you ask and how to solve them?
Continue to ask questions through supplementary conditions.
1. There were 72 people in the skating rink in the morning, 44 people left at noon, and 85 people arrived. How many people are skating now?
2. The Ice and Snow World received 987 people in 3 days. According to this calculation, how many people are expected to receive in six days?
Wait a minute.
Communicate in groups first, and then communicate with the whole class.
It is suggested that students can supplement their own conditions.
Second, new funding.
1. Four people in the group hand out the answers to the questions on the blackboard.
Guide the students to answer the questions on the blackboard, and ask them to list the comprehensive formulas in their exercise books for unbalanced calculation.
2. Talk to each other in groups. How did you solve it?
Teachers patrol and guide students to narrate.
3. Class report: organize the class to report, complement each other, and pay attention to the description of the meaning expressed in each step.
( 1)7 1-44+85
=27+85
= 1 13 (person)
7 1-44 indicates how many people are left after 44 people left at noon. With the arrival of 85 people, how many people are left in the skating rink now.
(2)987÷3×6 6÷3×987
=329×6 =2×987
= 1974 (person) = 1974 (person)
In the first method, 987÷3 calculates the reception number of "Ice and Snow World" 1 day, and multiplies it by 6 to calculate the total reception number for 6 days. (In fact, it is the original mixed application problem of multiplication and division. It is generally a mixed application problem of multiplication and division to find the total amount without knowing the single quantity. )
The second method, because it is calculated in this way, the number of people received every day can be regarded as the same, so we can first calculate how many times six days is three days, and the total number of people received in six days is also several times that of three days. You can directly multiply the 987 people in three days by twice the calculated number. Wait a minute.
Guide students to further understand the meaning of "according to this calculation".
Key point: Line drawing can be used to help you understand.
Teachers should pay attention to the description of this method, which does not require all students to master, but mainly to master the operation sequence.
Consolidation exercise
(1) Write the questions according to the information provided by the teacher. Add, subtract and mix. Getting on and off the bus, borrowing and returning books from the library, b speed, unit price, work efficiency.
Fill in the questions first, and then communicate with each other.
Work in groups to reduce repetitive exercises.
(2)P5/ Do it 1，2
Three. abstract
Students report the content of this lesson.
We solved many problems in this course. What have you gained?
Teachers selectively write books on the blackboard according to students' returns. (especially regarding the sequence of operations)
The operation sequence is based on the existing knowledge, which is convenient for students to recall and summarize.
Fourth, homework
P8/ 1—4
Blackboard design:
Four operations (1)
1. There were 72 people in the skating rink in the morning and 44 people left at noon. 2. "Ice and Snow World" received 987 people in three days. According to this
Another 85 people arrived. How many people are skating now? How many people are expected to receive in 6 days?
72-44+85 ( 1)987÷3×6 (2)6÷3×987
=27+85 =329×6 =2×987
= 1 13 (person) = 1974 (person) = 1974 (person)
Operation order: in the formula without brackets, if there is only addition and subtraction,
Or just calculate multiplication and division from left to right.
Summary after class:
The second class:
Teaching content:
P6/ Example 3 P 10/ Example 4 (including two-stage operation or mixed operation with brackets)
Teaching objectives:
1. Through two levels of operation, students can further master the operation sequence.
2. Let students experience the process of exploring and communicating to solve practical problems, and feel some strategies and methods to solve problems.
Learn to solve some practical problems with two-step calculation method.
3. In the process of solving practical problems, make students develop study habits such as careful examination of questions and independent thinking.
Teaching process:
First, the theme map introduction
Observe the theme map, find out the conditions and ask questions.
Guide students to observe the theme map. What do you see in the picture? What math questions would you ask?
Second, new funding.
According to the questions raised by students, give an example 3. On Sunday, my parents took Lingling to the "World of Ice and Snow". How much is the ticket?
The students answered the question in their exercise books.
Two people at the same table talk about how they solved it.
Report: The teacher writes it on the blackboard according to the students' report.
( 1)24+24+24÷2
=24+24+ 12
=48+ 12
=60 (yuan)
24÷2 is the price of children's tickets, which is half price, so 24÷2 is used, and the first two 24 are the total price of two adult tickets for mom and dad. Two adult tickets and one child ticket are the amount they need to buy tickets.
(2)24×2+24÷2
=48+ 12
=60 (yuan)
24×2 is the total price of two adult tickets for mom and dad, and Lingling's child ticket is 24÷2, and then adding the prices of the three tickets together is the total fare.
We solved the same problem in different ways. What are the characteristics of these two comprehensive formulas?
These two comprehensive formulas have no brackets, and there are addition, subtraction, multiplication and division in the formulas.
What is the operation sequence of such a comprehensive formula?
Students summarize the operation sequence.
Buy three adult tickets and pay 100 yuan. How much should I get back?
Wait a minute.
Example 4 morning tourists in the ice sculpture area 180, 270 pm. If every 30 tourists need a cleaner, how many more cleaners will be sent in the afternoon than in the morning?
Discuss in groups and finish independently.
Talk to each other in groups. How did you solve it?
Report.
( 1)270÷30- 180÷30
=9-6
=3 (Name)
270÷30 Work out how many cleaners need to be sent in the morning; 180÷30 Calculate how many cleaners need to be sent in the afternoon, and then calculate how many more cleaners need to be sent in the afternoon than in the morning by subtraction.
(2)(270- 180)÷30
=90÷30
=3 (Name)
270- 180 Calculate how many more visitors there are in the afternoon than in the morning, and then divide by 30 to calculate how many more cleaners are sent in the afternoon than in the morning.
Guide students to observe the differences between the two calculations and the different operation sequences.
Student summary.
The teacher writes on the blackboard according to the students' summary.
Third, consolidate the practice.
P7/ Do it 1，2
P 1 1/ do (after finishing the book, you can change the conditions, such as "buy 2 gloves" and so on. )
Teachers should master students' key languages in the process of practice to consolidate their knowledge.
Fourth, homework
P8-9/5-9
Blackboard design:
Four operations (2)
On Sunday, my parents took Lingling to the "Ice Sculpture Area in the Frozen Morning". Visitor 180, 270 p.m.
How much does it cost to buy a ticket to play in heaven and earth? If every 30 tourists need a cleaner, they need one in the afternoon.
(1) 24+24 ÷ 2 (2) 24× 2+24 ÷ 2 How many more cleaners were sent than in the morning?
=24+24+ 12 =48+ 12 ( 1)270÷30- 180÷30 (2)(270- 180)÷30
=48+ 12 =60 (yuan) =9-6 =90÷30
=60 (yuan) =3 (name) =3 (name)
Operation order: in the formula without brackets, there are multiplication and operation order; In the formulas with brackets, you must calculate them first.
Division, addition, subtraction, multiplication and division must be calculated first. Face.
Summary after class:
The third category:
Teaching content:
P 1 1/ Example 5 (strengthening the role of brackets), sum up the operation order.
Teaching objectives;
1. Make students further master the operation sequence of two-level operation and correctly calculate the three-step problem.
2. Strengthen the role of brackets in students' minds.
3. Summarize the order of elementary arithmetic in practice.
Teaching process:
First, review the introduction.
Recall the contents of the first two lessons and review the four operating sequences you have learned.
We have learned several different four operations before, remember? Who can tell me which four operation sequences you learned in the last lesson?
Write on the blackboard according to the students' answers.
Second, new funding.
Example 5
( 1)42+6×( 12-4)
(2)42+6× 12-4
Students answer independently in their exercise books. (Draw a sequence line)
Two students are performing on the blackboard.
The whole class took the exam.
The numbers, symbols and numerical order in the above two questions have not changed. Why are the calculation results of the two questions different?
We have been talking about "four operations" these days. What exactly are the four operations?
The students expressed their views on this issue.
Summary: Addition, subtraction, multiplication and division are called four operations. (blackboard writing)
Who can help you summarize the operation order of the four operations we have learned?
Students can answer freely.
Third, consolidate the practice.
P 12/ Do it 1, 2
P 14/4
The teacher patrolled to correct.
Fourth, homework
P 14— 15/2、3、5—7
Blackboard design:
Four operations (3)
(1) 42+6× (12-4) (2) 42+6×12-4 Operation sequence:
=42+6×8 =42+72-4 (1) In the formula without brackets, if
=42+48 = 1 14-4 Only add and subtract or only multiply and divide, both of them.
=90 = 1 10 should be calculated from left to right.
(2) in the formula without brackets, there are multiplication,
Division, addition, subtraction, multiplication and division must be calculated first.
(3) If there are brackets in the formula, they should be included first.
Inside the number.
Addition, subtraction, multiplication and division are called four operations.
Summary after class:
The fourth class:
Teaching content:
P 13/ Example 6 (Operation of 0)
Teaching purpose:
Make students master the problems that should be paid attention to in 0 operation.
Teaching emphases and difficulties:
0 cannot be divided into reasons.
Teaching process:
First of all, introduce oral calculation.
Fast oral calculation
Show:
( 1) 100+0=
(2)0+568=
(3)0×78=
(4) 154-0=
(5)0÷23=
(6) 128- 128=
(7)0÷76=
(8)235+0=
(9)99-0=
( 10)49-49=
( 1 1)0+3 19=
( 12)0×29=
Second, new funding.
Classify the above oral calculations.
Please talk about the operation of 0 according to the classification results.
Students classify and summarize the operations around 0.
The teacher writes on the blackboard according to the students' answers.
Is there anything else you want to ask or say about the operation of 0?
Students ask whether 0 is divisible.
Group discussion: Can 0 be divided?
The whole class debated. Explain your reasons separately.
Teacher's summary: 0 is inseparable. If 5÷0, it is impossible to get the quotient, because no number can be multiplied by 0 to get 5.0÷0, and it is impossible to get a definite quotient, because any number multiplied by 0 will get 0.
Three. abstract
Students summarize the problems that should be paid attention to in 0 operation.
Teachers guide students to sum up.
Fourth, homework
P 15— 16/8— 13
Blackboard design:
On the operation of "0"
100+0 =100 235+0 = 235 A number plus 0 returns the original number. Is 0 divisible?
0+319 = 3190+568 = 5680 cannot be divided.
99-0=99 154-0= 154 Subtract 0 from a number to get this number.
0×29=0 0×78=0 Multiply a number by 0 or multiply a number by 0 to get 0.
Divide 0÷76=0 0÷23=0 0 by a non-zero number to get 0.
49-49=0 128- 128=0 The minuend is equal to the minuend, and the difference is 0.
The teaching content of "decimal addition and subtraction" teaching design in the next semester of mathematics in the fourth grade of primary school;
People's education publishing house, fourth grade elementary school mathematics, volume 2, decimal addition and subtraction, pages 95-97
Teaching objectives:
1. Knowledge and skills: connect with real life and create situations. Let students explore the calculation method of decimal addition and subtraction independently and solve practical problems.
2. Process and method: cooperation and communication, summarizing the general methods of decimal addition and subtraction, and understanding the principle of decimal point alignment.
3. Emotion, attitude and values: new knowledge comes from life and serves life.
Teaching emphasis: written calculation method of decimal addition and subtraction
Teaching difficulty: understanding the principle of decimal point alignment
Teaching process:
First, review the old knowledge.
Calculate first, then check 246+48= 347-39=
Calculation rules of integer addition and subtraction
1, aligned with the same digits, and added and subtracted from the unit.
2. Whoever adds up to 10 will go forward 1, and if it is not reduced enough, it will go back from the last one 1.
Second, teach new lessons.
1, passionate introduction, questions.
Teacher: Please look at the big screen: At the 2004 Athens Olympic Games, China's Lao Lishi and Li Ting won the women's 10 meter platform doubles final. The courseware shows the final report form.
Teacher: What information did you learn from it? After the exchange, ask the students: According to this information, can you ask some questions about addition and subtraction? Write the corresponding questions on the blackboard according to the students' answers:
(1) How many points did China lead in the first round?
53.4-49.8=
(2) How many points did China lead in the second round?
58.2-49.2=
(3) What is the total score of China team in two rounds?
53.4+58.2=
(4) What is the total score of Canada in two rounds?
49.8+49.2=
(5) How many points did China lead in the two rounds?
2. Reveal the topic.
Teacher: Please observe these addition and subtraction formulas carefully. Do you find anything special about them? (There are decimals in all formulas)
How to add and subtract decimals? This is what we are going to learn today. (blackboard title: decimal addition and subtraction)
Step 3 explore
(1) Decimal subtraction (1 inquiry)
(1), calculate
Teacher: How many points did China lead in the first round (53.4-49.8)? Can you calculate? Please try it first.
(2) Say
Teacher: How do you calculate it? Compare your algorithm with your deskmate. Is it the same?
Teacher: Exchange your ideas in the group.
(3) discuss it.
Teacher: How many algorithms does your group have? Which is more suitable?
Let's talk about it in class. What is reasonable and simple?
(Compare the algorithms used by students. Please explain the thinking process in detail. )
Blackboard writing:
53.4
- 49.8
3.6
(4) Summary algorithm
When calculating decimal subtraction vertically, the decimal points of two decimal places should be aligned, and then the numbers on the same digit should be subtracted.
Try to practice: (solving problem 2)
58.2-49.2=
(2) Fractional addition
(1), give it a try
Teacher: Just now we discussed the subtraction of decimals, so how to calculate the addition of decimals? Please solve problems (3) and (4) independently.
(2) communication
Teacher: Tell your deskmate your algorithm gently. Come on, how did you calculate it? What difficulties have you encountered?
(3) Q.
Teacher: Why should the decimal points be aligned when calculating decimal addition vertically?
(4) Summary
Teacher: What did you learn from your study just now?
Blackboard writing:
53.4 49.80
+ 58.2 + 49.20
1 1 1.6 99.00
(3) Solving problems
Teacher: How many points did China lead in two rounds? How to calculate?
(Students think independently and finish)
Teacher: Would you please introduce your algorithm to the class?
Method 1: 53.40+58.20 =111.6; Method 2: 53.40-49.80=3.6.
49.80+49.20=99; 58.20-49.20=9.
111.6-99 =12.6 points 3.6+9= 12.6 points.
Teacher: What's the difference between these two algorithms?
Which method do you prefer?
Try to calculate the following questions. 12.4+24.36= 7.8 1-3.735=
Before calculation, there is no number to which "0" can be added.
(4) The group tries to summarize: What should we pay attention to when adding and subtracting decimals?
Report: decimal addition: When the column is vertical, note: the digits are aligned, starting from the low position, and the decimal point is at the midpoint of the result. Supplement: The calculation results should be simplified. Decimal subtraction: digit alignment, subtracting digits from the low order. If it is not enough, the previous number will be subtracted ... and then the decimal point will be added to the result. There is a 0 at the end of the decimal part of the number. Generally, 0 should be deleted. Before calculation, there is no number to which "0" can be added.
Summary: To calculate decimal addition and subtraction, first align the decimal point of each number (that is, align the number on the same digit), then calculate according to the law of integer addition and subtraction, and finally align the decimal point on the horizontal line of the obtained number. Note: In order to facilitate the comparison of statistical scores, 0 is not excluded from the above data.
There are times in life when you don't need to delete 0. Who can give an example? (on the price tag)
(5) Checking calculation
Calculate 5.64- 1.78 6.07+4.89.
The calculation of decimal addition and subtraction is easy to make mistakes. Is there any way to check the calculation results?
The calculation method of decimal addition and subtraction is the same as that of integer addition and subtraction. Addition can swap the positions of addends, or be tested by adding and subtracting another addend. Subtraction can be added and subtracted by difference or subtracted by minuend. For example.
Third, consolidate the practice.
1, calculation check 2.98+0.5612.53+4.67 7.2-6.45 5-0.41.
In our daily life, in fact, we have been dealing with decimals. Where else in life can decimals be used frequently? (shopping)
Xiaoming is a child who loves sports. On Sunday, his father took Xiaoming to the sports mall to buy things. I bought a pair of sports shoes for 38.5 yuan and 4.8 yuan's skipping rope. How much did they spend? Dad paid the salesman 50 yuan, how much should he get back? Will you solve it? Do a longitudinal calculation.
Fourth, the job design:
Textbook P98 exercises 16 (1 and 2).
Verb (abbreviation of verb) course summary
What did we learn in this class? If it were you, what would you like to remind everyone to pay attention to when calculating?
Induction: both decimal addition and subtraction and integer addition and subtraction should add and subtract the numbers in the same counting unit respectively, and both should start counting from the low place. When calculating decimal addition and subtraction, the decimal points should be aligned, and finally the decimal points on the horizontal line should be aligned in the molecule, and the decimal points should point to.
Teaching design of simple operation in the next semester of mathematics in the fourth grade of primary school: page 39 of the textbook, example 1
Teaching objectives:
1, let students know the simple calculation method of continuous reduction in solving life problems and experience the diversification of calculation methods.
2. Cultivate students' awareness and ability to choose algorithms according to specific conditions, and develop the flexibility of thinking.
3. Let students feel the connection between mathematics and real life, and use what they have learned to solve simple practical problems.
Teaching emphasis: understand the operation of different algorithms in continuous decline.
Teaching preparation: multimedia courseware
Teaching process:
First, create situations and introduce new lessons.
Teacher: Students, where did you go during the winter vacation?
Second, group cooperation, exploring new knowledge
1, show the situation map. (Multimedia presentation)
Teacher: This is a good season for an outing. Uncle Li is going to travel. Before he left, he wanted to consult the information. Please look at it. What information can you learn from the picture?
The book Self-help Tour has 234 pages.
Uncle Li read 66 pages yesterday and 34 pages today.
Q: How many pages are left?
Teacher: Will the students solve this problem? Then try it.
2. Group exchange report.
Teacher: What do you think?
The first solution: 234-66-34 (subtract what you read yesterday from the total number of pages, and then subtract what you read today. )
The second solution: 234-(66+34) (first calculate how many pages you read yesterday and today, and then subtract them from the total number of pages. )
The third solution: 234-34-66 (subtract what you read today from the total number of pages, and then subtract what you read yesterday. )
Teacher: The students solved the problem in different ways. Please choose one of these three formulas to calculate.
3. communication.
How did you calculate it?
4. elf (animated character) summary.
By solving the problem, we can see that there are many ways to calculate continuous reduction. Can be calculated from left to right in turn; You can also add up the subtractions and remove them from the minuend; You can also subtract the last subtraction first and then the previous one. We can choose an appropriate algorithm to calculate continuous reduction according to the characteristics of data in the formula. (Blackboard Title: Simple Operation)
5. Now I change 234 to 266. Think about it. Why do you think the calculation is simple?
(Students think and answer)
Third, consolidate the practice.
1, compare, whose method is simple.
62 1-82- 18 560- 178-22 756- 189- 156
2. The original 7 1 1 kg apple of Limin Fruit Shop has sold 476 kg, which is 24 kg bad. How many kilograms of good apples are left?
3. The practical problems that can be solved by continuous reduction calculation are put forward.
Fourth, the elf summed up the class
In the process of using different methods to solve problems, students have learned different methods of continuous subtraction calculation, and they can skillfully apply mathematical knowledge to their lives. I hope you can pay more attention to and observe, find and solve more mathematical problems and gain more mathematical knowledge.
Teaching design of multiplication operation law in the next semester of mathematics in the fourth grade of primary school I. Teaching content
The new curriculum standard textbook of People's Education Press, the third volume of mathematics in the fourth grade of primary school, 33 -35 pages, the first lesson of multiplication algorithm.
Second, the teaching objectives
⑴ Students experience the summation process of multiplicative commutative law and associative law, and perceive the method of "conjecture-verification".
⑵ Students can understand and master multiplication, commutative law and associative law, express the arithmetic in different ways, and use the arithmetic to solve simple problems.
⑶ Students feel the process and strategy of solving problems and improve their ability to solve problems. Have a new knowledge and understanding of mathematics.
Third, the focus of teaching
Students can understand and master multiplication, commutative law and associative law, express arithmetic in different ways, and use arithmetic to solve simple problems.
Fourth, teaching difficulties.
Students experience the summation process of multiplicative commutative law and associative law, and perceive the method of "conjecture-verification".
Verb (abbreviation of verb) teaching method and learning method
Because the teaching content of this class is very problematic and exploratory, I adopted the teaching strategy of organizing inquiry learning activities. Strive to cultivate students' consciousness and ability to solve problems while summarizing the operation rules through "guess-verification".
Sixth, the teaching process.
(1) Create situations and ask questions;
"Students, do you know when March 12 is?"
What are the benefits of planting trees?
In today's lesson, we will find and summarize the operation rules in multiplication by solving problems related to tree planting.
(2) conjecture verification, summing up the law;
1, and explore the law of multiplication commutation based on guidance.
(1) Guess
(Showing the theme map) "Please observe the mathematical information on the map carefully. Can you propose a mathematical problem solved by one-step multiplication? " (Students ask, the teacher writes it on the blackboard)
"Do you have different recipes?" (Two blackboard writing formulas. )
"We have listed two different formulas for the same problem, but the result is the same. Then we can say 25×4=4×25. " (blackboard formula)
Observe this formula and tell me what you find in your own words.
"Through such a formula, we found that the two factors exchanged positions and the product remained unchanged. Then, we just put forward a guess. Can this rule be applied to all multiplications? We need further verification.
⑵ Verification conjecture
Come on, how are you going to verify this rule?
(3) draw a conclusion
Report.
Conclusion: Through the conjecture and verification just now, it can be confirmed that the law we found is not accidental, and it can be applied to all multiplications.
(blackboard writing: multiplicative commutative law)
"Can you express multiplication and method of substitution in letters?"
⑷ Summary: We discussed the multiplicative commutative law. Please recall how we summed up multiplication and method of substitution just now.
Guide students to answer: first solve practical problems-discover laws-guess-verify with examples-and draw conclusions.
2. Explore the multiplicative associative law independently.
According to the "friendly tips", explore and learn independently.
(1) makes an activity request.
(2) student activities.
(3) The report is summarized and written on the blackboard.
(4) The multiplicative associative law is expressed by letters.
Third, consolidate the application and expand the summary.
(1) Basic exercises
1, do it after the book 1 topic.
You can guess the number behind the kitten according to the law of multiplication. Two questions on page 37 (guess, tell me which algorithm to use. )
(2) Comprehensive exercises
Show me the elf problem and tell me what you find. (communication, report)
Summary: the law of exchange is the law that two numbers add and exchange positions, and two numbers multiply and exchange positions. The associative law is the law that three numbers add or multiply to change the operation order.
(3) Expanding exercises
Finish question 2.
1. Put forward a mathematical problem of two-step multiplication and solve it independently?
report
Summary: When calculating the multiplication of three numbers, the product is first integer ten, integer hundred and integer thousand, so the calculation is simple.
Fourth, class summary.
Recall the content of this lesson and tell me what you have gained. What have you learned? How to get it and how to find it. )