1, the perimeter of the rectangle = (length+width) ×2C=(a+b)×2.

2. The circumference of a square = side length ×4 C=4a.

3. Area of rectangle = length× width S=ab

4. Square area = side length x side length s = a.a = a.

5. Area of triangle = base × height ÷2 S=ah÷2.

6. parallelogram area = bottom x height S=ah

7. trapezoidal area = (upper bottom+lower bottom) × height ÷ 2s = (a+b) h ÷ 2.

8. Diameter = Radius× 2D = 2r Radius = Diameter ÷2 r= d÷2

9. The circumference of a circle = π× diameter = π× radius× 2c = π d = 2π r.

10, area of circle = π× radius× radius.

1 1, triangle area = base × height ÷2. The formula S= a×h÷2.

12, square area = side length × side length formula s = a× a.

13, area of rectangle = length× width formula s = a× b.

14, area of parallelogram = base× height formula s = a× h.

15, trapezoidal area = (upper bottom+lower bottom) × height ÷2 formula S=(a+b)h÷2.

16, sum of internal angles: sum of internal angles of triangle = 180 degrees.

17, cuboid volume = length× width× height formula: V=abh.

18, cuboid (or cube) volume = bottom area × height formula: V=abh.

19, volume of cube = side length × side length × side length formula: V=aaa.

20. The circumference of a circle = diameter × π formula: L = π d = 2π r.

2 1, area of circle = radius× radius× π formula: s = π R2.

22. Surface (side) area of cylinder: The surface (side) area of cylinder is equal to the perimeter of the bottom multiplied by the height. Formula: S = CH = π DH = 2π RH Surface area of a cylinder: The surface area of a cylinder is equal to the perimeter of the bottom multiplied by the height plus the area of the circles at both ends. Formula: S=ch+2s=ch+2πr2.

23. Volume of cylinder: The volume of cylinder is equal to the bottom area multiplied by the height. Formula: V=Sh

24, the volume of the cone = 1/3 bottom x product height. Formula: V= 1/3Sh

15, the law of addition and subtraction of fractions: add and subtract fractions with denominator, only add and subtract numerators, and the denominator remains unchanged. Fractions of different denominators are added and subtracted, first divided, then added and subtracted.

26. Multiplication of fractions: use the product of molecules as numerator and the product of denominator as denominator.

27. The law of division of fractions: dividing by a number is equal to multiplying the reciprocal of this number.