1+ 1 1= 12 2+ 1 1= 13 3+ 1 1= 14 4+ 1 1= 15 5+ 1 / kloc-0/= 16 6+ 165438+ 0= 17 7+ 1 1= 18 8+ 1 1= 19 9+ 1 1=20

1+ 12= 13 2+ 12= 14 3+ 12= 15 4+ 12= 16 5+ 12= 17 6+ 12= 18 7+ 12= 19 8+ 12=20

1+ 13= 14 2+ 13= 15 3+ 13= 16 4+ 13= 17 5+ 13= 18 6+ 13= 19 7+ 13=20

1+ 14= 15 2+ 14= 16 3+ 14= 17 4+ 14= 18 5+ 14= 19 6+ 14=20

1+ 15= 16 2+ 15= 17 3+ 15= 18 4+ 15= 19 5+ 15=20

1+ 16= 17 2+ 16= 18 3+ 16= 19 4+ 16=20

1+ 17= 18 2+ 17= 19 3+ 17=20

1+ 18= 19 2+ 18=20

1+ 19=20

Subtraction formula within 10-20:

1 1- 1= 10 1 1-2=9 1 1-3=8 1 1-4=7 1 1-5=6 1 1 -6=5 1 1-7=4 65438+ 0 1-8=3 1 1-9=2 1 1- 10= 1

12-2= 10 12-3=9 12-4=8 12-5=7 12-6=6 12-7=5 12-8=4 12-9=3 12- 10=2

13-3= 10 13-4=9 13-5=8 13-6=7 13-7=6 13-8=5 13-9=4 13- 10=3

14-4= 10 14-5=9 14-6=8 14-7=7 14-8=6 14-9=5 14- 10=4

15-5= 10 15-6=9 15-7=8 15-8=7 15-9=6 15- 10=5

16-6= 10 16-7=9 16-8=8 16-9=7 16- 10=6

17-7= 10 17-8=9 17-9=8 17- 10=7

18-8= 10 18-9=9 18- 10=8

19-9= 10 19- 10=9

20- 10= 10

Extended data:

10 to 20:

"Add nine and subtract one, add eight and subtract two, add seven and subtract three, add six and subtract four, and add five and subtract five."

Take "plus nine MINUS one" as an example. "Add nine and subtract one" refers to the addition of a number and 9, and the number minus 1 is the unit of their sum.

For example: 8+9= () take 8 and subtract 1 to get 7, and use 7 as the unit of summation, that is, 8+9= 17, 5+9= () take 5 and subtract 1 to get 4, and use 4 as the unit of summation, that is, 5+9 =/kloc-. The method of "eight minus two, seven minus three, six minus four and five minus five" is the same as above.

And how can students master the abdication subtraction within 20 years in a short time? In fact, abdication subtraction within 20 is the opposite of carry addition within 20, that is, abdication subtraction within 20 is converted into addition within 10.

The formula is: "minus nine plus one, minus eight plus two, minus seven plus three, minus six plus four, minus five plus five."

How to use the formula? Take "minus nine plus one" as an example. "Minus nine plus one" means a number minus nine, and the result of adding 1 to this number is their difference.

For example, 17-9 = () take the 7th place of 17, and add 1, and the result is 8, that is, 17-9 = 8, 13-9 = () take/kloc-.

For example: 17-2 = () Distinguish between single digits and ten digits. Let's see if the single digits can come down first. If 7-2 is enough, subtract it with 10, remember 7 in your mind, then count down 6 and 5 to get 5, and then 1 in ten digits remains unchanged, and get 15.

The method of "minus eight plus two, minus seven plus three, minus six plus four, minus five plus five" is the same as "minus nine plus one".