2. Subtraction plus difference method: Subtracting the integer of subtree and adding the difference between subtree and integer equals the difference.
3. Difference between two complements: two complements are subtracted, and the minuend is subtracted by 50 times 2; Subtract three complements and be subtracted by 500 times 2; Four complements are subtracted, and the subtracted 5000 is multiplied by 2, and so on.
4. The sum of two digits is reversed: the ten digits of a number plus its single digits multiplied by 1 1 equals the sum.
Extended data:
Decimal method is: when the unit is not reduced enough, subtract the subtraction with 10 and add the remainder to the unit, that is, decimal method.
Break the ten-law formula
To put it simply, the "method of adding to ten" is the calculation problem of converting the carry addition within 20 into 10+N, which belongs to an arithmetic method from difficult to simple, such as the simple version of the "rule of adding to 10" of 7+3= 10, such as the relatively difficult 8.
In the eyes of Mann Loepke, a child research expert, "bare-backed numbers can't understand mathematics". Parents can easily learn mathematical operation ability by combining 10 rule.