Decimal method: As the name implies, it is to add two numbers first, and the result is 10. This is a simple operation that children can easily accept.

For example: 6+9= 15, 9 can be divided into 4 and 5, first add 6+4= 10, and then use 10+5= 15.

Decimal method: As the name implies, it is to decompose a large number into the sum of two numbers, one of which is 10, and turn it into a simple operation that children can easily accept.

For example, 17-8=9, and 17 can be divided into 10 and 7. First calculate 10-8=2, and then calculate 2+7=9.

Add operation

1, add two numbers with the same sign, take the same sign as the addend, and add the absolute values.

2. Add two numbers with different signs. If the absolute values are equal, the sum of two numbers with opposite numbers is 0; If the absolute values are not equal, take the sign of the addend with the larger absolute value and subtract the smaller absolute value from the larger absolute value.

3. Add two numbers with opposite numbers to get 0.

4. Adding a number to 0 still gets this number.

You can add two opposite numbers first.

6. Numbers with the same sign can be added first.