1. additive commutative law and associative law: By exchanging the positions of two numbers or changing the order of addition, the calculation process can be simplified.
2. Conversion from subtraction to addition: Conversion from subtraction to addition, for example, a-b can be converted into a+(-b) and then calculated.
3. Multiplication and distribution law: a number multiplied by the sum of two numbers is equivalent to this number multiplied by these two numbers and then added.
4. Multiplication multiple relation: multiply a number by 10, 100, 1000, etc. Moving the decimal point can simplify calculation.
5. Convert division into multiplication: convert division into multiplication, for example, A÷bcan be converted into a×( 1/b), and then calculate.
6. Simplification of fractions: Simplifying fractions into the simplest form can be achieved by finding the greatest common divisor of numerator and denominator.
7. Square difference formula: The relationship between the difference between two numbers and the square of their sum can be calculated by using the square difference formula.
8. Cubic difference formula: The cubic difference formula can be used to calculate the relationship between the difference of two numbers and their cubes.
9. Complete square number: By observing the characteristics of numbers, some complicated calculations can be converted into the form of complete square numbers, thus simplifying the calculation.
10. Fast estimation: by observing the size and order of magnitude of the number, fast estimation is carried out, so as to obtain the value close to the accurate result.