Teaching objectives:
1, through sorting out the process of abdication subtraction table within 20 years, further understand the relationship between formulas, and initially try to express the sorting process in simple language.
2. Further consolidate the calculation of abdication subtraction within 20.
3. In the process of sorting, experience the method of sequential thinking, realize that there are different sorting methods according to different standards, feel the fun of sorting, and improve the interest in learning mathematics.
Teaching emphasis: students learn to arrange subtraction tables in an orderly manner.
Teaching difficulties: discover the laws between formulas and learn to think in an orderly way.
Preparation of teaching AIDS: cards and courseware.
Teaching process:
First, oral arithmetic practice, introducing new lessons.
1, training exercise (3 groups)
Tell me what you found.
3. Dialogue: Naughty and laughing often have verbal contests. The computing cards they use are messy. Let's help them solve the problem together, shall we?
Second, start sorting and find the standard of sorting.
1. Share one point at the same table and sort out the cards.
2. Introduce various classification methods and find out the classification standards.
3. Teacher's summary.
Third, organize the tables and feel the connection between the formulas.
1. Students independently complete the subtraction table on page 17 in the book.
2. Show the subtraction table filled in by the students.
3. Guide students to find the law of formulas, feel the relationship between formulas and develop a sense of numbers. (Looking horizontally, vertically and obliquely ...)
Fourth, expand practice and learn to use the law.
( )-( )=9 14-( )=( ) ( )-7=( )
Fifth, talk about the harvest and exercise students' language expression ability.