Area of triangle = base × height ÷2. Formula S= a×h÷2 square area = side length× side length formula S= a×a rectangular area = length× width formula S= a×b parallelogram area = bottom× height formula S= a×h trapezoid area = (upper bottom+lower bottom) × height ÷2 formula s = (a+b) cuboid volume. Formula: S = = DH = 2RH 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+2r2 Volume of a cylinder: The volume of a cylinder is equal to the area of the bottom multiplied by the height. Formula: V = V = volume of SH cone = bottom × product height. Formula: law of addition and subtraction of V=Sh fraction: 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. The multiplication of fractions is: use the product of molecules as numerator and the product of denominator as denominator. The law of division of fractions: dividing by a number is equal to multiplying the reciprocal of this number. Unit conversion (1)1km =1km =1000m1m =1decimeter1decimeter =1cm/km. 8+0 square decimeter = 100 square centimeter 1 square centimeter = 100 square millimeter (3) 1 cubic meter = 1000 cubic meter = 1 cubic meter. 00 kg 1 kg = 1000 g = 1 kg = 1 kg (5) 1 hectare = 10000 m2 1 mu = 666.666 m2. Quantity relation of +0 cubic centimeter 1. Unit price × quantity = total price 2. Single output × quantity = total output 3. Speed × time = distance 4. Efficiency × time = total work 1. Arithmetic 1. Additive commutative law: Two numbers are added to exchange the position of the addend, and the sum remains the same. 2. The law of addition and association: When three numbers are added, the first two numbers are added first, or the last two numbers are added first, and then the third number is added, and the sum remains 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, or the second two numbers are multiplied first, and then the third number is multiplied, and the product remains unchanged. 5. Multiplication and distribution law: When two numbers are multiplied by the same number, you can multiply the two addends by this number respectively, and then add the two products, and the result remains unchanged. Such as: (2+4) × 5 = 2× 5+4× 5. 6. Nature of division: In division, the dividend and divisor are expanded (or reduced) by the same multiple at the same time, and the quotient remains unchanged. Divide 0 by any number other than 0 to get 0. 7. Equation: An equation in which the value on the left of the equal sign equals the value on the right of the equal sign is called an equation. Basic properties of the equation: When both sides of the equation are multiplied (or divided) by the same number at the same time, the equation is still valid. 8. Equations: Equations with unknowns are called equations. 9. One-dimensional linear equation: An equation with an unknown number of 1 is called a one-dimensional linear equation. Example method and calculation of learning linear equation of one variable. That is, an example is given to illustrate that the formula is replaced by χ and calculated. 10. Score: divide the unit "1" into several parts on average, and the number representing such a part or points is called a score. 1 1. 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. 12. Comparison of fraction size: Compared with the fraction of denominator, the numerator is large and the numerator is small. Compare the scores of different denominators, divide them first and then compare them; If the numerator is the same, the denominator is big and small. 13. Fractions are multiplied by integers, and the product of the multiplication of fractions and integers is a numerator, and the denominator remains unchanged. 14. Fractions are multiplied by fractions, the product of numerator multiplication is numerator, and the product of denominator multiplication is denominator. 15. Fraction divided by integer (except 0) equals fraction multiplied by the reciprocal of the integer. 16. True fraction: The fraction with numerator less than denominator is called true fraction. 17. False fraction: the fraction with numerator greater than denominator or numerator equal to denominator is called false fraction. False score is greater than or equal to 1. 18. With score: write the false score as an integer, and the true score is called with score. 19. The basic nature of the fraction: the numerator and denominator of the fraction are multiplied or divided by the same number at the same time (except 0), and the size of the fraction remains unchanged. 20. A number divided by a fraction is equal to the number multiplied by the reciprocal of the fraction.