1, arithmetic of addition and subtraction:

-additive commutative law: a+b = b+a

-additive associative law: (a+b)+c = a+(b+c)

-Definition of subtraction: a-b = a+(-b)

2. Multiplication and division algorithm:

-multiplicative commutative law: a × b = b × a

-Law of multiplicative association: (a × b) × c = a × (b × c)

-Multiplicative distribution law: a × (b+c) = (a × b)+(a × c)

-definition of division: a ÷ b = c, where a = b× c.

3, the relationship between numbers:

-sequence relation: greater than (>) and less than (

-The relation of the opposite number: a+(-a) = 0.

4, digital algorithm:

Properties of -0: a+0 = a, a × 0 = 0.

The properties of-1:a×1= a.

(2) Formulas for calculating the perimeter and area of graphics.

1, square: perimeter c, area s, side length a.

Perimeter = side length ×4, C=4a

Area = side length × side length, s = a× a.

2. Cube: the volume is V and the side length is A..

Surface area = side length × side length× 6, S=a×a×6.

Volume = side length × side length × side length, v = a× a× a.

3. Rectangular: perimeter c, area s and side length a..

Circumference = (length+width) ×2, C=2(a+b)

Area = length × width, S=ab

4. cuboid: volume v, area s, length a, width b and height h.

Surface area (length× width+length× height+width× height )× 2, S=2(ab+ah+bh)

Volume = length × width × height, V=abh

5. triangle: the area is s, the base length is a, and the height is H.

Area = bottom × height ÷2, S=ah÷2.

Height of triangle = area ×2÷ base of triangle = area ×2÷ height

6. parallelogram: the area is s, the base length is a, and the height is H.

Area = bottom × height, S=ah

7. Trapezoid: the area is S, the upper bottom is A, the lower bottom is B, and the height is H.

Area = (upper bottom+lower bottom) × height ÷2, S=(a+b)× h÷2.

(3) Unit conversion

1, length unit conversion

1 km =1000m.

1 m = 10 decimeter.

1 decimeter = 10/0cm.

1 m = 100 cm。

1 cm = 10/0mm.

2, area unit conversion:

1 m2 = 100 hectare.

1 hectare = 1 10,000 square meters.

1 m2 = 100 square decimeter.

1 square decimeter = 100 square centimeter.

1 cm2 = 100 mm2.

3, the body (volume) product unit conversion:

1 m3 = 1000 cubic decimeter.

1 cubic decimeter = 1000 cubic centimeter.

1 cubic decimeter = 1 liter.

1 cm3 = 1 ml.

1 m3 = 1000 liter.

4, weight unit conversion:

1 ton = 1000 kg.

1 kg =1000g.

1 kg = 1 kg.

5. RMB unit conversion:

1 yuan = 10 angle.

1 angle = 10 point.

1 yuan = 100 integral.

6. Time unit conversion:

1 century = 100 year.

1 year = 65438+ February.

The big month (3 1 day) includes: 1, 3, 5, 7, 8,10,65438+February.

Abortion (30 days) includes: April, June, September,165438+1October.

February 28th in a normal year and February 29th in a leap year.

365 days in normal year; A leap year has 366 days.

1 day =24 hours, 1 hour =60 minutes.

1 minute =60 seconds, 1 hour =3600 seconds.

It is worth noting that the formula can't be memorized, and it needs a lot of practice in the topic to really master it!