The decimal addition table within 20 is shown below.

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

Extended data:

For addition within 20, it is easier to add it to 10.

Simple formula:

19 19 years of good friends,

Hand in hand,

3737 is so close,

Let's go together, four, four, six, six,

Make a pair of hands in half.

Solution thinking

1. Remember "9 to 1", "8 to 2", "7 to 3", "6 to 4" and "5 to 5".

2. The method of filling ten is simple and easy, and the thinking process includes "looking at large numbers, dividing by two, filling ten by three, and adding four".

3. Look at large numbers, divide them into decimals, make up ten, and add the remainder.