1, add up to ten method: look at large numbers, divide them into decimals, add up to ten, and calculate. For carry addition within 20, the decimal method is to divide the smaller number into several numbers and several numbers, use the larger number and one of them to make ten, and then add several to ten to get a result greater than ten. The ten-break method is aimed at carry-free addition and subtraction within 20.

2, break ten method: look at the decimal, divide by the large number, break ten, count. The ten-break method is aimed at carry-free addition and subtraction within 20.

Non-carry addition within 20: divide a dozen into ten digits and ten digits, add an addend to the separated decimal, and then add the result to 10.

Subtraction of abdication within 20: If the subtrahend is greater than the number in the subtrahend unit, write 10 on the side close to the subtrahend subtract the result of the subtrahend add it to the number.

Importance of addition and subtraction within 20

Addition and subtraction within 20 is the basis of mathematical calculation in primary schools and the key to improve the calculation ability. If the addition and subtraction within 20 are very skilled, you only need to master new knowledge points when learning the addition and subtraction within 100. The addition and subtraction of two digits refers to the addition and subtraction of single digits and ten digits within 20 respectively. This is true whether it is carry addition or abdication subtraction.

How to learn addition and subtraction within 20 years directly affects the development of computing power. However, if the calculation fails, the children's mathematics academic performance will be unsatisfactory, which will also affect their interest and confidence in mathematics learning. If you add or subtract within 20, you must be proficient in saying numbers when you see formulas. It lays a solid foundation for the calculation of large numbers in senior grades.