The formulas of the first and second volumes of the sixth grade are: additive commutative law: A+B = B+A; Additive associative law: (a+b)+c = a+(b+c); Multiplicative commutative law: ab = ba Multiplicative associative law: (AB) C = A (BC); Multiplication and distribution law: a (b+c) = ab+AC. Rectangular perimeter = (length+width) × 2; Square perimeter = side length × 4; The circumference of a circle = π× diameter = π× radius× 2. Area of rectangle = length × width; Area of a square = side length × side length; Area of parallelogram = base × height; Area of triangle = base × height ÷ 2; Trapezoidal area = (upper bottom+lower bottom) × height ÷ 2; Area of circle = π× radius; Annular area = external circular area-internal circular area; Surface area of cuboid = (length× width+length× height+width× height) × 2; Average speed = total distance/total time; Meet distance = speed and x meet time, meet time = meet distance ÷ speed and; Discount = current price/original price (discount < 1), current price = original price × discount, original price = current price/discount; Example scale = distance on map ÷ actual distance, actual distance = distance on map ÷ scale, distance on map = actual distance × scale; Catch-up distance = speed difference × catch-up time, catch-up time = catch-up distance/speed difference.