When subtracting a few, divide a dozen into ten and a number, subtract a few from ten and add the number to the divisor.
The abdication subtraction of more than a dozen points in the second volume of senior one mathematics is14-5 =18-9 =1-2 =12-3 =13-4 =/kloc-.
14-5 = 18-9 = 1 1-2 = 12-3 = 13-4 = 15-6 = 16-7 =
18- 1. 18-2. 18-4. 18-5. 18-6. 12-5. 19-
18-9 =11-2 =12-3 =13-4 =15-6 =16-7 =/kl
Do you want to tell them that the first grade math should be vertical? Of course. These are two methods. Can be taught on the basis of students' understanding.
The first grade focuses on the addition and subtraction within 20, which is carried out on the composition of numbers. Ten is the key.
How to add a few to 10, add a few to a dozen in the first grade and the corresponding subtraction? Evaluate the class from the aspects of teaching objectives, difficulties, teachers' class implementation and teaching methods adopted by teachers.
Math 9 in senior one plus some calculations. Try 10 addition and 10 subtraction. How about volume two, 9 plus a few 10?
9+0=
9+ 1=
9+2=
9+3=
9+4=
9+5=
9+6=
9+7=
9+8=
9+9=
9 minus 10.
9-0=
9- 1=
9-2=
9-3=
9-4=
9-5=
9-6=
9-7=
9-8=
9-9=
Review the first grade mathematics subtraction courseware of PEP before class;
1 1-5 16-8 17-9 29-9 78-70 36-4
There are six cute little animals here, waiting for you to take them around the world of mathematics! As long as you speak your mind out loud and calculate correctly, you can be its good friend! (Team Award: Prepare Small Blackboard)
Who can represent 36-4 with a stick?
First, the scene import:
Drawings showing box P67 1 (lower two rows of commodity display cabinets)
Teacher: Students, many small shops have opened today. Let's go and have a look! What do you see? how much is it?
If you have 8 yuan and want to buy one of them, is it enough? How much is it? How did you work it out?
Second, explore new knowledge:
1, raising questions.
8-8 12-8 15-8 35-8 (according to the students' answers, choose the questions related to Example 2 and write them on the blackboard)
The problems found by the students are the same as those encountered by Xiaoming in the book! Please open your books P68 and see if we can find a way to help Xiaoming.
Step 2 show the theme
Teacher: How to set the formula? What are the similarities between 36-8 and the previous question (36-4)? What is the difference? (……)
Teacher: The students' observation ability is really strong. Today, we are going to learn how to subtract one digit from two digits. One digit is not enough. (Refer to the blackboard: two digits minus one digit, and paste: "One digit is not enough")
Computer demonstration: 6-8 is not enough, what should I do? )
3. Explore the basic calculation method:
Teacher: Let's shake it with the stick on the table. (Students try to pose by themselves)
Teacher (demonstration): Now please ask a classmate to say, how to say it?
Teacher: Do you understand this classmate's method? He is very clever. He borrowed 10 from ten people. Is it enough to reduce 6 to 16 and 16-8? Please tell the two students at the same table again in this way.
Teacher: Now let another student talk about this method.
(report)
(conclusion)
Teacher: The students speak very well! Look at the blackboard, please. Play on the blackboard and complete the blackboard. Students write in the book. )
Computer demonstration: (explained by teacher). If you look at the formula without using a stick, can you say what you think?
Form a blackboard writing:
4. Explore other methods:
Teacher: Excuse me, is there any other way? (pendulum, talk, teacher board)
Choose an algorithm you like and say it yourself.
5. Summary: (Find the best way)
Teacher: The students are really interested. They came up with so many good ideas with a brainwave! In fact, when the number of digits is not enough, borrow 1 from the ten digits to make 10, and then reduce it. (Board: 10 Borrow ten to get one) This is the abdication subtraction of two digits minus one digit that we are learning today. (board: abdication subtraction)
6. Question:
Teacher: Is there anything you don't understand?
Third, consolidate the exercises:
1, feedback exercise: (Can you solve these problems in the way you just learned? )
(When finished, the students say what they think. )
2. Complete the second question "Do" on page 68. (Trial practice)
Please read the books P68 and 2. (First, the students calculate independently, and then the deskmate says it is reasonable and revised. )
3. Complete question 5 of exercise 12.
Students calculate independently first, and then revise the answers 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 their answers, so that they can further feel the process of abdication and reduction.
4. Additional exercises:
1) race;
2) You say I write.
5. Think about it: How much can I put in ()?
()()-6=()()
Fourth, summary.
Teacher: Please recall what we learned in this class.
Student: This lesson learned the abdication subtraction of two digits minus one digit.
Teacher: how to calculate the abdication subtraction of two digits MINUS one digit?
Student: Explain the calculation method in your own language.
Design of blackboard writing: two-digit MINUS one-digit gives way to subtraction
If the number of places is not enough, borrow one from ten to make ten and then reduce it.
1 1-5 36-8=28 36-8=28
16-8
12-4 29-3
78-8
36-4
First-year math, 5. How much is more than thirty plus more than fifty? Hello,
The answer is about 80.
Satisfied with the answer,
Please adopt,
Thank you.
What should we pay attention to in cooperative learning of mathematics in the first grade of primary school? Pay attention to discipline requirements and define tasks. The first grade of primary school is to lay a good foundation, and the basic operation plays a great role in future study. There is also the need to cultivate interest and make students happy to learn.