Textbook description

After the first two lessons, students have basically mastered the calculation method of carry addition. Appendices 5, 4, 3 and 2 of this section are all related to the first two sections and can be calculated by exchanging addends. The design of teaching materials requires students to complete these calculations with what they have learned.

Page 1 10 of the textbook "Review" to review the carry addition problems learned earlier. Prepare to calculate the addend of 5, 4, 3 and 2 by the exchange addend method.

Example 1 (page 1 10) has a picture of a teacher asking questions under 5+7=□ 5+8=□. It is intended to guide students to calculate numbers with 7+5 and 8+5, so that students can learn to exchange addends for calculation.

Example 2 (page110) only gives the formula. Ask the students to calculate the numbers of 4+8 and 3+9 with the learned 8+4 and 9+3, and consolidate the calculation of decimal addend with the exchange addend method.

On page 1 10, there are three exercises. Among them, each set of questions in question 2 and question 3 corresponds to each other from top to bottom, with Osuka decimals above and corresponding decimal increments below. This arrangement helps students to master the calculation method better.

Exercise 2 1 There are 4 exercises.

Question 1 has the same form as question 3 in exercise 19. Let the students practice adding a few words to 5, 4, 3 and 2, and get familiar with the calculation by exchanging addends.

The second question is a mixed exercise of 5, 4, 3, 2 plus a few and the learned subtraction. The topic "See who can calculate quickly and accurately" first appeared in this unit. Students are required not only to calculate correctly, but also to improve the calculation speed. Train students to calculate carry addition within 20 correctly and quickly, and improve their calculation ability.

Question 4 is a simple statistical table. This form of exercise first appeared in textbooks. Ask the students to do addition exercises with the numbers in the table. Its significance is to let students get in touch with statistical tables and infiltrate statistical ideas.

Teaching suggestion

1. This part can be taught in 3 classes. Teach 5, 4, 3 and 2, add a few words, carry out consolidation exercises and comprehensive exercises in class, and complete the exercises in exercise 2 1

2. Students prepare for calculation by exchanging addends.

Enrich 1 10 page "review". For example, add 6+5, 8+9, 7+8 ... Let students practice 9, 8, 7, 6 and add a few questions. After the exercise, take 8+9 and 7+8 equations as examples to guide students to sum up: exchanging addends can get the calculation formula of decimal number, and thinking about the number of decimal places can lead to the number. If some students use the "ten-complement method" to calculate, it is also possible.

3. Highlight the thinking process and cultivate the reasoning ability.

When teaching example 1 and example 2, pay attention to let students dictate the thinking process. For example, calculate 5+7 and think: 7+5= 12, so 5+7= 12. Let students cultivate their preliminary reasoning ability in the process of clearing their minds and getting familiar with thinking.

4. Strengthen practice and improve the calculation speed.

The calculation method of adding a few to 5, 4, 3 and 2 is easy to master. Mastering carry addition within 20 is also an important task in this teaching. In order to make students calculate correctly and skillfully, they must do necessary exercises. Arrange the addition questions within 20 decimal places properly, and make full use of the practice forms that students like in textbooks to arrange them properly in classroom teaching. Let the students practice actively and improve the calculation speed continuously. In practice, students with learning difficulties are counseled, and attention is paid to helping students simplify their thinking process and improve their calculation speed. For example, 9+4, think about it: 10, 13.

On the basis of practice, you need to explain to the students that you can think quickly in any way you want. After proficiency, the process of any method can be directly said step by step without thinking.

5. Exercise 2 1 Teaching suggestions for the fourth question.

The fourth question is the first statistical table. Let the students know the table before doing the problem, that is, the first vertical line of the table has a ball, a shuttlecock and a skipping rope; The second vertical row reads "one class has", and the following figures are the number of these three sporting goods in one class, that is, a class has seven balls, five badminton balls and four skipping ropes; The third vertical line says "One * * * has", which means that we are required to count how many balls, badminton and skipping ropes there are in Class One and Class Two. Then, let the students do it one by one and fill in the numbers in the book. Students with learning difficulties can be encouraged to ask questions before calculating. For example, class one has seven balls, class two has six balls and class one has several balls. Let the students clear their minds and understand the actual meaning of the problem, and the specific calculation will not be a problem.

6. After teaching the addition of 5, 4, 3 and 2, write the carry addition table within 20 on a big piece of paper, or you can write all the learned addition formulas on a big piece of paper and post them in the classroom for students to practice further.