The calculation is skillful. Students should cultivate the accuracy of calculation and the habit of using calculation skills reasonably from grade one. You can try to do this when calculating the addition and subtraction within 20.

Find out the best method of oral calculation

There are many kinds of oral calculation methods, and how to find the best oral calculation method is the key to improve the speed and accuracy of oral calculation. When practicing, you can review a variety of oral calculation methods with students, so that students can get the best method through comparison.

1, do subtraction, want to add. Do the inverse of addition with subtraction and think with addition. For example, 12-8, Xiang 8+( )= 12.

2. Violation of the Ten Laws. For example, 13-7 can be thought as follows: 10-7+3=6.

3. Continuous subtraction (commonly used method), such as 13-7. You can think of it as' continuous subtraction ': 13-3-4 = 6, which means dividing 7 by 3 and 4.

4. Supplementary methods. For example, 13-7 can also think like this: 13- 10+3=6.

Addition formula table

Addition formula within 10 1+ 1= 2? 1+ 2= 3 2+ 2= 4 ? 1+ 3= 4 2+ 3= 5 3+ 3= 6 ? 1+ 4= 5 2+ 4= 6 3+ 4= 7 4+ 4= 8 ? 1+ 5= 6 2+ 5= 7 3+ 5= 8 4+ 5= 9 5+ 5= 10 ? 1+ 6= 7 2+ 6= 8 3+ 6= 9 4+ 6= 10 ? 5+ 6= 1 1 6+ 6= 12 ? 1+ 7= 8 2+ 7= 9 3+ 7= 10 4+ 7= 1 1 ? 5+ 7= 12 6+ 7= 13 7+ 7= 14 ? 1+ 8= 9 2+ 8= 10 ? 3+ 8= 1 1 4+ 8= 12 ? 5+ 8= 13 6+ 8= 14 7+ 8= 15 8+ 8= 16 ? 1+ 9= 10 2+ 9= 1 1 ? 3+ 9= 12 4+ 9= 13 ? 5+ 9= 14 6+ 9= 15 7+ 9= 16 8+ 9= 17 ? 9+ 9= 18 ? 1+ 10= 1 1 ? 2+ 10= 12 ? 3+ 10= 13 ? 4+ 10= 14 ? 5+ 10= 15 ? 6+ 10= 16 7+ 10= 17 ? 8+ 10= 18 ? 9+ 10= 19 10+ 10=20?

The formula for addition within 20 is1+11=12? 2+ 1 1= 13 ? 3+ 1 1= 14 ? 4+ 1 1= 15 5+ 1 1= 16 ? 6+ 1 1= 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 9 = 0? 9-8= 1 ? 9-7=2 ? 9-6=3 ? 9-5=4 ? 9-4=5 ? 9-3=6 ? 9-2=7 ? 9- 1=8 8-8=0 ? 8-7= 1 ? 8-6=2 ? 8-5=3 ? 8-4=4 ? 8-3=5 ? 8-2=6 ? 8- 1=7 7-7=0 ? 7-6= 1 ? 7-5=2 ? 7-4=3 ? 7-3=4 ? 7-2=5 ? 7- 1=6 6-6=0 ? 6-5= 1 ? 6-4=2 ? 6-3=3 ? 6-2=4 ? 6- 1=5 5-5=0 ? 5-4= 1 ? 5-3=2 ? 5-2= 1 ? 5- 1=4 4-4=0 ? 4-3= 1 ? 4-2=2 ? 4- 1=3 3-3=0 ? 3-2= 1 ? 3- 1=2 2-2=0 ? 2- 1= 1 1- 1=0