Subtraction rule of numbers within ten thousand:
1, aligned with the same number;
2. Starting from the unit;
3. If the number on a number is not reduced enough, when it is 10, it will be subtracted from the previous number 1.
Simple algorithm: subtract a number close to the whole hundred from a number, first calculate the number close to the whole hundred into the whole hundred, then subtract a few and add a few.
Extended data
Subtraction follows several important patterns. It is anti-commutative, which means that changing the order will change the sign of the answer. It is not associative law, that is, when a subtraction exceeds two numbers, the order of subtraction is very important.
Subtracting 0 does not change a number. Subtraction also follows predictable rules related to addition and multiplication.
These laws can be proved, starting with the subtraction of integers and summarizing them with real numbers and other things. Continue the general binary operation of these patterns and learn in abstract algebra.