Knowledge points of "addition and subtraction within 100" in the first grade of primary school mathematics
1. Ten digits are added and subtracted, and one digit is added and subtracted. 1, carry-free addition 20+30=5067+2=6968+30=98.
2. Subtraction without abdication 80-50=3069-2=6798-30=68
Second, carry addition (add up to ten)
1, make up ten songs: one for nine, two for eight, three for seven, four for six and five for ten. (Note: Two figures rounded to ten are complementary.)
2.20 Carry-in addition: decimal method: 8+72= 15, ten digits plus 1, one digit minus the complement (2+8= 10, 2 is the complement of 8).
3. 100 plus 362+8=44 decimal extraction method: the digits are connected by arcs, and the digits are added to 1 and subtracted. (The method is the same as within 20)
Third, abdication subtraction.
1, abdication less than 20: ten-break method: 16 1-9=7 digits' complement.
Teaching plan of addition and subtraction in mathematics 100 in grade one of second primary school.
Teaching content: page 68 of the textbook, example 2, exercise 12, questions 5, 6 and 8.
Teaching objectives:
1, master the calculation method of abdication subtraction from two digits, and correctly calculate abdication subtraction.
2. Go through the process of exploring the calculation method of abdication subtraction of two digits MINUS one digit.
3. Feel the close connection between demise subtraction and real life, and realize the role of demise subtraction in life.
Key points and difficulties:
1, master the calculation method of abdication subtraction of two digits minus one digit.
2, encourage students to use a variety of methods to calculate.
Prepare teaching AIDS and learning tools:
1, the teacher prepares the scene diagram courseware.
2. Students prepare 3 bundles of 6 sticks.
Teaching process:
First, pre-school preparation
Do oral calculations. (according to the computer. Students practice driving a train)
1 1-3= 13-8= 17-9= 14-5=
15-7= 12-3= 16-8= 13-7=
Teacher's Dialogue: What did we learn last class? Let's ask some questions and tell us what you think.
38-6= 87-3= 96-6=
Teacher's words: change it to 38-9=, 87-8=, 96-8=, can you count? Look carefully. What did you find?
The students found that the number of double digits was smaller than the reduced number. If it is directly reduced, will it be enough? (Not enough) How to calculate these three questions? (abdication), in this lesson, we will learn the abdication subtraction of two digits MINUS one digit.
Blackboard writing: two-digit MINUS one-digit give way to subtraction
Second, explore new knowledge.
(1) Teaching Example 2.
1. Guide students to enumerate subtraction formulas from problem situations.
Courseware demonstration: pictures of toy shelves in toy stores.
Teacher: Last class, we learned how to solve the problem of "how much money is left after buying an elephant toy with 35 yuan money" according to the unit price of toys on the shelf. What other useful information does this picture tell us? Two toy cars under the shelf are highlighted on the screen.
Health: The map tells us that the prices of two toy cars are 15 yuan and 36 yuan.
The courseware continues to demonstrate: two children talk. The child on the left is asking, "I only have 8 yuan and want to buy a racing toy." How much do I have to deposit? "
Teacher: What are the two children in the picture saying and thinking?
Student: The child on the left said, I have 8 yuan, and I want to buy a toy car with a unit price of 36 yuan. How much should I deposit? The children on the right are thinking about how to figure out how much money to save.
Teacher: Do you know how to work out this formula? Why is this listed?
Answer the teacher's blackboard writing
36-8=
2. Guide students to explore calculation methods.
(1) Teacher: What's the difference between Type 36-8 and Type 35-2 and Type 76-4?
Health: formulas such as 35-2 and 76-4 are enough to reduce the number in the reduction unit; And the number in the unit 36-8 has not been reduced enough.
Teacher: What if the reduction is not enough? Wave it with a stick first.
Start shaking the stick and discuss the calculation method of 36-8 in groups.
(2) Guide students to talk about the stick insertion method in communication.
Teacher: Who will tell us about the process and method of sticking sticks in your group?
Health: 6 is not enough to subtract 8. Let's open a bundle first and combine it with the original 6 to form 16, and then subtract 8 from 16.
Teacher: 16 MINUS 8 leaves 8, plus the remaining 2 bundles (20) and one * * * leaves 28. Write the number "28" after the formula.
(3) Guide students to summarize the calculation methods.
Teacher: What did you find from the swing just now? Who can talk about the method of 36-8 according to the swing process?
Health: From the process of swinging just now, I found that when calculating 36-8, I can divide 36 by 20 and 16, then subtract 8 from 16, and finally add 8 and 20 to get the difference of 36-8.
(4) Guide students to explore other algorithms.
Teacher: Are there any other algorithms?
Health: 36 can also be divided into 26 and 10, 10 MINUS 8 to get 2, and then 26 plus 2 to get 28.
Teacher's summary: Just now, we used several methods to calculate the abdication subtraction of two digits minus one digit, which can be as simple as possible in the future calculation.
Third, consolidate the practice.
1. Complete the second question "Do" on page 68.
Let the students calculate independently first (you can specify students to calculate on the blackboard, and the rest can practice below), and then revise collectively.
When revising the answer, assign 1 to 2 questions, let the students talk about their own calculation process, and let them focus on thinking: what should I do if the number of digits is not reduced enough?
2. Complete question 5 of exercise 12.
Students calculate independently first, and then correct collectively. Let the students talk about the calculation process and method of 8 1-4 and 60-3 in combination with the process of revising the answers, so that the students can further feel the process of abdication and reduction.
3. Complete the exercise 12, question 8.
Let the students clearly calculate the task first, then calculate independently, and finally correct it.
Fourth, class summary.
Teacher: Please recall what we learned in this class.
Student: In this class, we learned the abdication subtraction of two digits minus one digit.
Teacher: how to calculate the abdication subtraction of two digits MINUS one digit?
Verb (short for verb) homework
Reflections on the teaching of addition and subtraction within 100 of mathematics in grade one of grade three primary schools
After this class, a teacher said that the topic assigned in this class was a bit difficult, and many students could not reach the level, only a few students could come up with it. Some teachers also said that the highlight of this class is the design of topics, which can arouse students' thinking, especially the design of four interesting topics, which is of great help to students' subsequent computing study. The range of calculation results can be determined by estimation to reduce the error caused by excessive deviation. The purpose of my teaching design is: 1. According to the learning situation in our class, many students are only willing to accept mechanically, rather than think with their brains. A little more complicated topics are more difficult, and they are unwilling to accept challenges in their study, and of course they can't appreciate the happiness brought by their study.
2. Make the calculation teaching not monotonous, mechanical and repetitive.
3. We should cultivate students' observation ability and thinking ability, cultivate students' orderly thinking ability, comparative analysis ability and divergent thinking ability, and improve their learning level.
4, through the guidance and demonstration of some excellent students, let other students imitate.
There are indeed difficulties for students with learning difficulties in class, but there are also surprises brought by students with strong expressive ability and flexible thinking. Through the teaching and collective evaluation of this course, I think it is impossible for an open class to distract students' thinking and improve their thinking ability and listening habits. Teachers need to prepare lessons carefully in the usual teaching process, make an objective evaluation of students' learning situation, and formulate a teaching design suitable for students in this class.