One or four operational formulas
1. additive commutative law: Two numbers are added, the position of the addend is exchanged, and the sum is unchanged.
2. The law of addition and association: When three numbers are added, the first two numbers are added first and then the third number, or the last two numbers are added first and then the first number, and the sum is unchanged.
3. Multiplication and exchange law: when two numbers are multiplied, the position of the exchange factor remains unchanged.
4. Multiplication and association law: When three numbers are multiplied, the first two numbers are multiplied by the third number, or the last two numbers are multiplied by the first number, and the product remains unchanged.
5. Distribution law: the sum of two numbers is multiplied by a number, which can be multiplied first and then added.
Second, the measurement and measurement formula
1. Length unit conversion: 1 m = 10 decimeter =100 cm =1000 mm.
2. Area unit conversion: 1 square meter = 100 square decimeter = 10000 square centimeter = 1000000 square millimeter.
3. Volume conversion unit: 1 m3 = 1000 cubic decimeter = 1000000 cubic centimeter = 10000000 cubic millimeter.
4. unit of volume conversion: 1 liter = 1000 ml = 10000 cubic centimeter = 1000000 cubic millimeter.
Third, the geometric figure formula
1. Triangle area formula: S=ah÷2 (where A is the base length and H is the height).
2. parallelogram area formula: S=ah (where a is the base length and h is the height).
3. Rectangular area formula: S=ab (where A and B are two sides of the rectangle).
4. Formula of square area: S=a? (where a is the side length of a square).
5. Trapezoidal area formula: S=(a+b)h÷2 (where A and B are the lengths of the upper and lower bases of the trapezoid and H is the height of the trapezoid).
Four, statistical chart formula
1. Frequency distribution table: used to represent the frequency (frequency of occurrence) distribution of a group of data.
2. Broken line statistical chart: used to indicate the changing trend of data.
3. Bar chart: used to compare data values of different categories.
Five, life application formula
1. The relationship between speed, time and distance: speed = distance ÷ time, time = distance ÷ speed, distance = speed × time.
2. Calculation of interest: interest = principal × interest rate× time, and principal = interest/interest rate× time.
3. Calculation of tax rate: tax = tax rate × (income tax allowance).
4. Discount calculation: discount = (original price-current price) ÷ original price.
These formulas are the important contents of the first volume of the third grade mathematics course. Mastering these formulas is helpful to improve students' ability to apply mathematics and solve practical problems. In the process of learning, we should strengthen practice and master these formulas skillfully to lay a solid foundation for future study.