When calculating the abdication subtraction of 100, it should be noted that the unit is not enough. Borrow 1 from ten digits, and the unit is 10 minus a few. If the ten digits are not enough, borrow 1 from the one hundred digits, and the ten digits are 9 MINUS a few.

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.

The calculation method is as follows:

24- 15 vertical

24

- 15

——————

first step

Click a little on 2 to count as a loan.

Second step

Imagine 4 as the calculation of 14 (0 is a placeholder, for example, and the second step is omitted in practice).

Third step

2 becomes 1 after it is borrowed, and then it is calculated (a 0 of a bit means that the calculation is completed, and the 0 of the result occupies a bit, which is actually written as a bit, and the occupied one is not written).

Fourth step

Get the result (final writing)

Subtraction of abdication within 20

1 1-9=2

1 1-8=3

1 1-7=4

1 1-6=5

1 1-5=6

1 1-4=7

1 1-3=8

1 1-2=9

12-9=3

12-8=4

12-7=5

12-6=6

12-5=7

12-4=8

12-3=9

13-9=4

13-8=5

13-7=6

13-6=7

13-5=8

13-4=9

14-9=5

14-8=6

14-7=7

14-6=8

14-5=9

15-9=6

15-8=7

15-7=8

15-6=9

16-9=7

16-8=8

16-7=9

17-9=8

17-8=9

18-9=9

reference data

Liu Ye. Basic oral calculation. Harbin: Harbin Publishing House, 20 16.