1. Add decimal integer:
For the addition of two integers with ten digits, first add the single digits to get the single digits (if the sum is greater than 10, it will be carried), and then add the ten digits to get the final result. For example: 34+40=74.
2. Subtraction of integer ten:
For the subtraction of two integers of ten, first subtract the single digits to get the single digits (if the minuend is less than the minuend, borrow from the ten digits), and then subtract the ten digits to get the final result. For example: 67-30=37.
3. Round up the integers and add them:
Add two numbers, and if one of them is difficult to calculate, you can adjust it to a more easy number. For example, 88+27 can be adjusted to 90+25= 1 15, and then subtract 2 to get the final result 1 13.
4. Subtraction of abdication:
When subtracting, if the unit number needs to borrow from the tenth place, you can subtract 1 from the unit number, add 10 to the tenth place, and then subtract. For example: 43-28, you can abdicate to 42- 18 to get the final result of 24.
5. Forward and backward are addition and subtraction:
In addition and subtraction, if the sum of single digits and ten digits exceeds 10, carry it; If the single digits are not reduced enough, you have to abdicate. For example: 56+38, first calculate the unit number 6+8= 14, round to 4, then calculate the decimal number 5+3+ 1=9, and the final result is 94.
6. Complement addition:
When adding, you can make one of the numbers into an integer ten and then add them up. For example: 36+ 17, you can add 17 to 20 to get 36+20=56, and then subtract 3 to get the final result of 53.
7. Even increase and decrease:
When calculating the addition and subtraction of continuous numbers, we can simplify them by using the law of numbers. For example, 1+2+3+4+...+ 100 can be divided into 50 pairs, namely (1+100)+(2+99)+(3+98)+...+(50) Using these skills flexibly can improve the calculation speed and accuracy.