1. algorithm: 1, additive commutative law a+b=b+a 2, additive associative law (a+b)+c=a+(b+c) 3, multiplicative commutative law a×b=b×a 4, and multiplicative associative law (a× b) × c = The subtraction property a-b-c=a-(b+c) 2, and the division property a÷b÷c=a÷(b×c) 3. Perimeter calculation formula 1, rectangular perimeter calculation formula C=2(a+b) or C=2a+2b 2, square. Square area calculation formula S = the square 3 of a, parallelogram area calculation formula S=ah 4, triangle area calculation formula S=ah÷2 5, trapezoid area calculation formula S=(a+b)h÷2 (trapezoid bit line length calculation formula m=(a+b)÷2 leads to another formula S=mh, in the new version. 5. The formula 1 about the circle, and the formula d=2r 2 about the length of radius and diameter. Supplement: Other formulas of the circle may be included in other versions of textbooks. For example, the formula for calculating the circumference of a circle is C=2πr or C=πd, the formula for calculating the area of a circle is S=π r squared six, the formula for calculating the volume of a cuboid is 1, the formula for calculating the volume of a cuboid is V=abh 2, the formula for calculating the volume of a cube is cubic seven and the formula for calculating the surface area is 1. The formula for calculating the surface area of a cuboid is S = 2 (square eight of the formula for calculating the surface area of AB+AH cubes is S=6a, others: the formula for calculating the volume of a cylinder is V=π r squared h or V=Sh (S is the bottom area of a cylinder), the formula for calculating the volume of a cone is V=π r squared h÷3 or V=Sh÷3, and the formula for calculating the sector area is S=n/360 πr squared (N is a sector). In practical application, other formulas transformed from them are needed. For example, calculating the length of a long square requires A = S÷bis, so I won't write them all here. 3. There is also the concept of the essence of equality, only words without formulas. Four. 1. mass unit conversion 1 ton = 1 000kg1kg =1000g 2. Distance relationship distance = speed x time (S=vt) problem: awesome.