(1) Complement+Complement = and-one addend = another addend (2) Minus-Minus = Difference-Difference = Minus+Minus = Minus (3) Factor × Factor = Product ÷ One Factor = Another Factor (4) Divider ÷ Divider = According to the meaning of the ratio, the ratio can be obtained; The method of comparison: divide the former by the latter term. The basic nature of the ratio: the first and last items of the ratio are multiplied or divided by the same number (except 0), and the ratio remains unchanged. The basic properties of the ratio can be used to simplify the ratio. Among the four operations of elementary arithmetic, addition and subtraction are called primary operations, and multiplication and division are called secondary operations. (2) If the formula without brackets only contains operations at the same level, it should be calculated from left to right once; If there are two levels of operation, do the second level operation first, and then do the first level operation. (3) In the formula with brackets, the brackets should be counted first. If there are both brackets, count the brackets first, then the brackets, and finally the brackets. 39. The unit "1" of the score and percentage application problem is known, so use multiplication. The unit "1" is unknown. Use division. (1) What percentage of a number is another number? Basic formula: What is the fraction (1%) or multiple of a number when finding the previous number ÷ the next number (comparison quantity ÷ standard quantity) ②? (The unit "1" is known) Basic formula: the quantity of the unit "1" × the fraction = the quantity corresponding to the fraction ③ Know what the percentage of a number is and find this number. (The unit "1" is divided or the equation is unknown) Basic formula: Fraction Ⅱ (4) gives two numbers, and find how many fractions one number is more than the other. Given two numbers, what percentage is one more than the other? Given two numbers, find out how many points one number is less than the other. Given two numbers, how much is one less than the other? Basic formula: the difference between the two numbers is the amount of "1" (standard amount principal: the money deposited in the bank is called principal. Interest: the excess money paid by the bank when withdrawing money is called interest. Interest rate: the percentage of interest in principal is called interest rate. ② Interest calculation formula: interest = principal× time× interest rate, interest tax = principal× time× interest rate× 5% 41. Additive commutative law: a+b = b+a, laws of addition and association: (a+b)+c = a+(b+c), laws of multiplication and exchange: ab=ba. Law of Multiplication and Association: (ab)c=a(bc) Law of Multiplication and Distribution: (A B) C = AC BC Operational Properties ① Basic Properties of Subtraction: A-(B+C) = A-B-C-B-C = A-(B+C) ② Basic Properties of Division: A ÷ B.× 22. Area of a square = side length × side length S = A. A = A. A = A 5, area of a triangle = bottom diameter = radius ×2 d=2r radius = diameter ÷2 r= d÷2 9, circumference of a circle = pi× diameter = pi× radius × 2C = π d = 2π r/. =πr 1 1, surface area of cuboid = (length× width+length× height+width× height )× 212, volume of cuboid = length× width× height V =abh 13, surface area of cube = side length. The surface area of cylinder = upper and lower bottom areas+lateral area s = 2π rH 18, and the volume of cone = bottom area × height ÷ 3v = sh ÷ 3 = π r h ÷ 3 = π (d ÷ 2) h ÷ 3 = π (c ÷ 2 . / Cubic v: volume a: surface area of side length = side length × side length× ×6 S table =a×a×6 volume = side length× side length V=a×a×a 3, rectangle c perimeter s area a side length perimeter = (length+width )× 2 c = 2 (a+b) area = length× width S. surface area. Volume = length × width × height V=abh 5 triangle s area a bottom h height area = bottom x height ÷2 s=ah÷2 triangle height = area × 2 ÷ bottom triangle bottom = area × 2 ÷ height 6 parallelogram s area a bottom h height × h ∏ 2 8 circle s area c circumference ∏. Bottom area r: bottom radius c: bottom perimeter (1) lateral area = bottom perimeter x height (2) surface area = lateral area+bottom area x 2 (3) volume = bottom area x height (4) volume = lateral area ÷ 2 x radius 10 cone v: volume h: height. Bottom area r: bottom radius volume = bottom area × height ÷3 Total number ÷ Total number = average sum and difference problem (sum+difference) ÷ 2 = large number (sum-difference) ÷ 2 = decimal and multiple problem ÷ (multiple-1) = decimal × multiple = planting trees. Then: number of plants = number of nodes+1 = total length ÷ plant spacing-1 = total length = plant spacing× (number of plants-1) plant spacing = total length \ then: number of plants = number of nodes = total length ÷ plant spacing = plant spacing. Then: number of plants = number of nodes-1 = total length ÷ spacing between plants-1 total length = spacing between plants × (number of plants+1) spacing between plants = total length ÷ (number of plants +0÷ difference between two distributions = number of shares participating in distribution (. Meeting distance = speed × meeting time = meeting distance; The sum of speed and speed = meeting distance; Meeting time; Catch up with the problem; Distance = catch up with time; Distance; Speed difference = catching distance; Catch up with time; Downstream speed = (downstream speed+countercurrent speed) ÷2 Water flow speed = (downstream speed-countercurrent speed) ÷2 Solute weight+solvent weight = solution weight ÷ solution weight × 100% = concentrated solution weight × concentration = solute weight ÷ concentration = solution weight profit and discount profit. × 100% increase or decrease = principal× increase or decrease percentage discount = actual selling price ÷ original selling price× 1 00% (discount < 1) interest = principal× interest rate× time after tax interest = principal× interest rate× time × (1-) 29 days in leap year kloc-0/2: 365 days in average year and 366 days in leap year: 1 day =24 hours: 1 hour =60 minutes: 1 hour =60 seconds: 1 hour =3600 seconds product = bottom area.