Subtraction by abdication, a special mathematical term, can also be called subtraction by borrowing. That is, when two numbers are subtracted and the number of digits to be subtracted is not enough, borrowing the previous digit is equivalent to adding 10 to this digit, and then calculating.

Method 1: subtract the integer 10, that is, write the subtraction as 10 minus. For example, if 8 is written in the form of 10 minus 10-2, then the whole formula is 5 1- 10+2. Why did it become +2 here? Because 5 1- 10 has been reduced by 2, and 2 will be added later. The rest of the formula is easy to work out.

Method 2: The method of dividing the minuend into 10 is to divide the minuend into how many plus 10. For example, 5 1 can be divided into 40+ 10, and then 8 is the whole formula. Children first calculate 10-8, then calculate 4 1+2, and the result is 43.

Method 3: Borrowing or borrowing 10 is actually the most correct method. It uses dozens of additions and subtractions to divide the minuend. For example, decompose 5 1 into 40+ 1 1, and then subtract 8. Let the children calculate 1 1-8 first, and then calculate 40+3, and the result is 43. This is also to prepare for the next method.

Method 4: Vertical method. This is the most commonly used method in mathematical calculation. This method clearly tells children the concept of unit and ten digits, ten digits MINUS ten digits, and one digit MINUS one digit. It is not difficult to understand by combining the previous methods.

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