1, the basis of subtraction calculation: subtraction of single digits and ten digits.
Mathematical calculation requires basic knowledge of addition and subtraction, and when children are faced with such things as "15-3", the best way to deal with it is simply to subtract the sum of the unit and the decimal digits respectively to get the result. That is: 5-3 = 2, 10-0 = 10 (where the ten digits can be reserved directly), which adds up to 12.
2. The calculation basis of subtraction with more than two digits: the numerical score with more than 10.
In the number learning of primary school mathematics, children will be exposed to the content of the number fraction, that is, a number can be divided into several and several combinations, for example, 5 can be divided into 0 and 5, 1 and 4, 2 and 3.
When 10 is above, we need to let children know that every number above 10 can be a score of 10 and x, such as 15, and can have a score of 10 and 5.
3. "Borrowing ten methods" in subtraction calculation.
Mastering the numerical score above 10, children can use the "borrowing ten method" in subtraction calculation to complete subtraction calculation with various subtraction units larger than the minuend unit. Through the calculation method of ten, the subtraction within 20 can be simply converted into the addition and subtraction within 10. Let's explain a practical application, taking 12-9 as an example.
The numerical scores of a. 12 can be written as: 10 and 2.
B. Subtract with 10 and 9: 10-9= 1.
C. Add the remaining 2 and 1: 2+ 1=3.
So, the result is 12-9=3. This is the application process of "borrowing ten methods" in the whole subtraction, and it is the focus of children's high-level subtraction calculation.
Mathematics teaching needs to establish mathematical logical thinking for children.
Mathematics is different from other subjects. When children are first exposed to mathematics, it is even more necessary to establish abstract mathematical logic for children, so that children can get the correct way of thinking and problem-solving ideas in mathematics learning. However, many parents neglect to teach their children how to establish such logical thinking, and instead let them calculate in the simplest way.
And this way is nothing more than "counting your fingers." Many parents think that children can master mathematical calculations by hand index or counting. In fact, by counting fingers, counting money and raising money, children are still in the stage of counting and still have not stepped into the scope of calculation.