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Decimal method: a mathematical calculation method, that is, when the number of digits is not reduced enough, subtract the subtraction with 10 and add the remainder to the number of digits, that is, decimal method.

For example: 1 1-4, 1-4 digits are not enough for reduction, so subtract 4 from11(10+1),10.

Subtraction formula: minus nine plus one, minus eight plus two, minus seven plus three, minus six plus four, minus five plus five, minus four plus six, minus three plus seven, minus two plus eight.

In the primary school stage, the main thing is actually the child's computing ability, and the computing ability can actually be cultivated by some methods, such as adding ten or breaking ten. As long as the primary school is properly trained and its computing ability is not too great, then children will not have much problem in math learning.

The idea of making up ten or breaking ten is very simple, that is, taking 10 as the standard, making up several differences, making up several differences and adding them up. 9 to 1, 8 to 2, 7 to 3, 6 to 4 and 5 to 5.