Ten MINUS five, four, three, two.

course content

Page 17 of the textbook, exercise 4, questions 1 and 2. Impart objective knowledge and skills.

(1) enables students to further understand the arithmetic of subtracting a few from a dozen, and can correctly subtract five, four,

3, 2' s oral calculation.

(2) Cultivate students' observation ability, calculation ability and the ability to ask and solve problems.

Force. Process and method

Through the formation process of subtracting 5, 4, 3 and 20 calculation methods, we have experienced the exploration of problem solving and the diversity of problem solving methods. Emotional attitudes and values

Learn mathematics while solving problems, so that students can realize the value of learning mathematics and cultivate their interest in learning. Important and difficult

Key points: Understand the arithmetic of subtracting five, four, three and two from more than ten, and be able to do the oral calculation of subtracting five, four, three and two from more than ten correctly.

Breakthrough method: adopt the method of independent inquiry and cooperation and exchange.

Difficulty: understanding of the abdication subtraction method of more than ten MINUS five, four, three and two. Breakthrough method: autonomous learning, encouraging algorithm diversity.

Teaching methods and learning methods

Teaching method: guided inquiry method

Learning methods: autonomous learning and cooperative communication. Teaching process 1. Introduce a new lesson

Do students like animals? Guess what animal the teacher likes best? (Student guesses) The teacher likes little monkeys best. Today, I also invited the little monkey Beibei. Look, everyone, is Beibei cute? Do you want to be friends with Beibei? Then I have to do Beibei a little favor first. It turns out that the monkey mother gave Beibei such a difficult problem. Let's have a look.

The courseware shows a group of cute puppies playing on the grass. Some puppies got tired of playing and went back to the small house. How many puppies are there on the grass now? (5) So how many puppies have returned to the small house? Second, explore the examples and explore the algorithm.

(1) There are 7 puppies in the small house. How did you know?

Student observation report: * * There are 12 puppies, and now there are 5 puppies on the grass, 12-5=7 (only), so 7 puppies have returned to the small house.

The teacher wrote on the blackboard in time 12-5=7 and asked: What do you think? Talk to your deskmate about your thoughts. Group cooperation, communication and reporting. There may be several ideas:

zero

110-5 = 5,5+2 = 7, so 12-5=7. zero

25+7= 12, so 12-5=7. zero

3 12-2 = 10, 10-3 = 7, so 12-5=7. ..... the algorithm of teachers writing blackboard books for students in time. (In order to improve the enthusiasm of students to speak, each algorithm is named after the first child. As long as it is right, the teacher should fully affirm everyone's idea: children really think! There are really seven puppies at home. You are right!

(2) Continue to explore the method of subtracting five, four, three and two from one dozen.

The teacher draws six formulas of Example 4 on the blackboard. First, organize the students to try to calculate the results in their own way in the group.

The teacher asked: How did you work it out? Can you introduce it to us?

Students go to the podium to show their calculation results and tell their own algorithms, which other students can supplement.

Teacher's summary: Now we have so many ways to calculate a dozen MINUS several. Which algorithm do you like? Let's hold a small voting meeting, choose an algorithm we like and vote for the inventor who invented this algorithm first. Student activities.