The key of the equal ten method is to analyze that the unit is not reduced enough, and then decompose the subtraction into two numbers. Its calculation process:

14-9, unit 4 is not enough to subtract 9, so we subtract unit 4 first and it becomes an integer 10. At this time, we subtract 5 from this 10 (because 9=4+5), and the answer is 10-5=5. That is,14-9 =14-5 =10-5 = 5. Carry addition within 20

(1) Remember "9 to 1", "8 to 2", "7 to 3", "6 to 4" and "5 to 5". Take 15-8=7 as an example; Children are likely to use their fingers; Or small building blocks, etc. Subtract from 15 one by one; After subtracting 8; Found that there were seven left.

This algorithm is the most primitive and basic; But it takes the most time. Children can use this method at first; Because for the first grade children; They need to use some concrete and vivid things to help them perform concrete to abstract deduction; So many children will use their fingers or small building blocks to complete the calculation; This is a normal performance.

(2) The method of ten plus one is simple, and the thinking process includes "one look (at large numbers), dichotomy (at decimals), three plus ten, and four plus".

(3) Look at large numbers, divide them into decimals, add them to ten, and add the remainder.

3, abdication subtraction

(1) abdication subtraction should be kept in mind, starting from the unit;

(2) who is not enough to retreat, don't forget to add ten to the standard;

(3) If the interval is 1, it is best to remember that 0 is changed to 10.