Unit 2 addition within ten thousand teaching content: carry addition within ten thousand.
Teaching purpose:
1. enables students to thoroughly understand the calculation rules of pen addition within ten thousand, and can accurately calculate the addition problem of two-digit continuous carry by applying the rules.
2. Cultivate students' habit of studying hard and improve their calculation level.
Key points and difficulties:
When the last digit adds up to ten, you should input 1 to the previous digit, and when adding the previous digit, remember to add 1.
teaching process
Review for the exam and gain new knowledge.
basic skill
Oral calculation: 9+6 = 5+5 = 6+8 =
8+6+ 1=8+2+ 1=6+5+ 1=
Find the sum of 385 and 705.
The whole class practices together, the teacher makes a tour, and finishes the collective correction.
Can you write a two-digit addition formula yourself?
What should I pay attention to in the calculation without carry addition?
The same numbers are aligned.
Start with the unit.
The teacher emphasized that when the top number adds up to ten, you should use 1 to add the previous number, and when adding the previous number, remember to use 1 to add the added number.
Learn new lessons
Introduce new courses and topics.
Teacher: The review just now is the carry addition we just learned. The students have mastered it well. Today we continue to learn carry addition, but it is slightly different from what we learned before. Today, we are going to learn continuous carry addition.
Blackboard writing: continuous carry addition
Teaching examples 1
Students try to get 98+25 results with sticks (various methods are allowed. )
Discuss which method you like in groups to guide the study of methods in textbooks.
Ask questions:
Teacher: Which part to add first, and how to add the single root of 8 and 5? Eight sticks and how many sticks make 10 sticks? (8+2+3= 13)
10 can be tied into a bundle when it is full, tied up and hung up for everyone to see. Where can they be put? 10 1 bundle, that is, 1 10, is placed under the whole bundle of sticks.
Add a whole bundle of sticks, 9 bundles plus 2 bundles plus this 1 bundle, one * * *, and there are 12 bundles of sticks and three sticks. I pointed to the picture and asked: Where did this bundle of sticks come from?
Put single sticks together, and when it reaches 10, bundle them into a bundle and put them under the whole bundle of sticks.
Teacher's summary: A single root full of ten can be tied into a bundle and placed under the whole bundle, which is 1 10.
Column vertical calculation.
Students are free to write vertically and then discuss which is reasonable. How to write this question vertically? (One is aligned with one, and ten is aligned with ten. )
Which one should I add? (starting from the unit. )
So how do you write the number of digits added in the vertical position?
Think about it: how should I put the stick?
Complete the calculation independently. (Two students are performing on the blackboard, and the rest are doing it in their notebooks. )
Comments: Check whether the position of "1" is correct in the dictation at the same table, and whether 1 is omitted or forgotten when adding carry.
Do it.
1, calculated directly in the book, indicating students' collective performances and comments.
2. Find out the number of the formula on each carrot.
3, exercise 4, the first question, even a company.
4. Globe 85 yuan, schoolbag 48 yuan, how much does it cost to buy a globe and a schoolbag? What other questions can you ask?
The teaching content of the second lesson: 3 digits plus 3 digits continuous carry plus sign.
Teaching objectives:
Further cultivate students' estimation ability and estimation methods.
On the basis of mastering the two-digit continuous carry addition, further study the three-digit continuous carry addition.
Improve the speed and accuracy of students' calculation
Key points and difficulties:
When the last digit adds up to ten, you should input 1 to the previous digit, and when adding the previous digit, remember to add 1.
Teaching process:
First, review preparation and output new knowledge.
1, column vertical calculation
59+7785+6859+89
Q: Who remembers what to pay attention to when the two-digit continuous carry addition column is vertical? Have you noticed?
2, oral calculation
600+800900+ 100 1000+ 100
Step 3 estimate
599+800900+ 10 1989+ 1 12
Q: Can you quickly work out the approximate answer without writing? what do you think?
Second, learn new lessons.
estimate
Teacher: Just now, the students quickly estimated the approximate figures of the above three formulas by converting the figures into integers, which is also an estimation method. Let's estimate the number of a formula.
Reptiles 376
Amphibians 284
Teacher: Can you estimate the number of known reptiles and amphibians in China?
Four-person group discussion requires everyone to express their opinions and methods.
Teacher: Which integer is closest to 376? (400)
Teacher: Which integer is 284 closest to? (300)
Q: How many kinds of reptiles and amphibians are known in China? (700)
Q: Do you think it will be more than 700 or less than 700 if calculated accurately? Why?
(376 is less than 400 and 284 is less than 300, so their sum must be less than 700)
Write an arithmetic problem
Teacher: Please make an accurate calculation in vertical order to see how many kinds of reptiles and amphibians are known in China.
Assign students to perform and comment in groups.
The teacher stressed: when the number on the digit adds up to ten, you need to add 1 to the previous digit, and don't forget to add 1 when calculating to the previous digit.
Solid development
Teacher: Through the study of two classes, we not only mastered the continuous carry addition, but also learned the species number of reptiles and birds, reptiles and amphibians in China. In fact, there are many wild animals in China. Please open the textbook 15 and tell us what quantitative relationship you found in the table.
Students can freely find out the quantitative relations in the table, form problems and solve them side by side vertically.
Do it.
Do it on page 18 of the textbook, and students can do it independently.
The teaching content of the third class: practice class
Teaching objectives:
Through review, students can further master the calculation rules of pen calculation and addition within ten thousand, and can apply the rules to calculate accurately.
Through teaching, we can learn to organize the learning methods of knowledge with the internal relations between knowledge, and cultivate students' ability of active exploration, bold imagination and cooperative communication.
Key points and difficulties:
Cultivate students to actively explore, boldly imagine, and cooperate and communicate.
teaching process
First, set the situation and reveal the content.
Teacher: There are many sailboats on the sea, and each sailboat has two boxes of articles. What should I do if I want to know how many items are loaded on the ship?
(Add up two boxes of articles)
Teacher: Today we are going to review the continuous carry addition within 10,000. Please open the textbook 19. Can you tell us roughly which ship has turned over the most things before accurately counting the number of items on board? Which ship has the least cargo? How do you know that? Can you tell everyone what you think?
Teacher: Please do a vertical calculation. Is the order of the six ships the same as you estimated?
Second, the textbook page 19, write the sum of the upper and lower addends directly in the table.
Teacher: Is there any way to accurately calculate the sum of the upper and lower addends without vertical columns on the manuscript paper?
3. Jingguang Center Building is the current skyscraper in Beijing, with a height of 209 meters, which is shorter than CCTV Building 196 meters. Do you know how high the CCTV building is?
Q: Which building in this question is tall? How to think about the problem?
Fourth, calculate the number of corn.
Fifth, unlock the game
There is a number on the lock and a formula on the key. Please connect the formula with the corresponding number.
Sixth, judge, question 7 on page 20 of the textbook, judge whether each question is wrong, and tell me where it is wrong.
Seven, 536, 9 15, 35 1, 85, 464, 208, 649, 873, 792, 127.
Which two numbers add up to 1000? Tell me what you think.
Eight, * * * * identical analysis 2 1 page, question 9.