First, cultivate the ability of addition and subtraction of primary school students within 20. Students learn the composition and decomposition of numbers within 10 as soon as they enter school, which is the basis of addition and subtraction within 10. Using the existing knowledge and experience, it is very easy for students to do addition and subtraction within 10. Then, the textbook guides students to know numbers within 20 and learn carry addition within 20. For carry addition within 20, I mainly use the method of adding ten to guide students to do oral arithmetic. Such as: 9+8=? Think about it: 9 and 1 add up to 10, 8 divided by 1 and 7, 10, plus 70% 17. Another example: 7+8=? Look at large numbers and divide them into decimals. Eight plus two equals 10. Divide 7 into 2 and 5. 10 plus 5 equals 15. It is easy to calculate the carry addition within 20 by decimal method.
The second semester of senior one focuses on cultivating students' ability of abdication and subtraction within 20 years. I instruct students to do ten-word calculations, such as: 17-9=? From the number of units, it is not enough to subtract 9 from 7, so the tenth place is 1 and the tenth place is 1, that is, 1 10 minus 9 equals 1, 1 plus 7 equals 8. The teachers in our grade group exchanged ideas and worked out a formula: one dozen MINUS 9, plus1; A dozen MINUS 8, a few plus 2; A dozen MINUS seven, a few plus three; A dozen MINUS six, a few plus four; A dozen MINUS five, a few plus five; A dozen MINUS four, a few plus six; A dozen MINUS three, a few plus seven, a dozen MINUS two, a few plus eight. Of course, the formula only applies to abdication subtraction within 20. Some students can add and subtract orally. Such as: 13-6=? Think: 6 plus 7 equals 13, so 13-6=7. We encourage students to do oral calculations in various ways.
Second, cultivate the ability of multiplication and division of the second grade students' oral table. You have to learn multiplication and multiplication formula in the first semester of senior two. It is necessary to guide students to understand the meaning of multiplication, let them know that multiplication is a simple operation of seeking the sum of addends, let them go through the process of compiling multiplication formulas, and let them understand the source of multiplication formulas through operations such as putting a pendulum and drawing a picture. In this way, students will memorize the multiplication formula. The multiplication formula is the basis of multiplication and division in the oral calculation table. Students memorize multiplication formulas on the basis of understanding, and it is easy to multiply and divide in the oral calculation table.
Third, cultivate the ability of addition and subtraction within 100% for third-grade pupils. Addition and subtraction within 20 is the basis of addition and subtraction within 100. If students have a solid foundation, they can do oral calculations directly; If students forget anything, they should first review the addition and subtraction within 20, and then practice the addition and subtraction within 100. Such as: 28+59=? In terms of single digits, 8 plus 9 equals17; If 1 is entered with decimal places, it will be written as 7; Decimal plus 2 plus 5, it is written as 8; Add 1 to 7 to write 8,28+59 = 87. Another example: 92-28=? From the unit, 2 minus 8 in the unit is not enough. If 1 is subtracted from 10, 1 in the unit is 10, and the sum of 10 and 2 in the unit is 12. 12 minus 8 equals 4. If you have several numbers, you can write 4 or 10.
Fourth, cultivate the ability of third-grade primary school students to multiply one digit by two digits and divide. The basis of multiplication and division of a single digit is the multiplication and division in the table and the addition and subtraction within 100. As long as the students have a solid foundation in oral calculation, it is no problem to multiply one digit by two digits. The multiplication and division method of calculating a single digit orally is the basis for learning the multiplication and division method of multiple digits later. Learning mathematics in primary school is like climbing stairs. Climb the first level, then the second level, then the third level. The same is true of verbal arithmetic. Can skillfully add and subtract within 20, skillfully multiply and divide in the table, and skillfully add, subtract, multiply and divide two digits within 100.
In a word, verbal calculation was not built in a day, and it needs constant practice. If every primary school math teacher can spare five minutes in the daily math class to practice oral arithmetic for students, then the students' oral arithmetic ability must be good from the lower grades. In addition, oral arithmetic should be carried out in various forms, such as helping small animals find homes, winning red flags, and comparing: who is the small pacesetter of oral arithmetic, and so on. Only by diversifying the forms of oral calculation can students' interest in oral calculation be improved and the expected results be achieved.