1. Decimal operation 1) Addition and subtraction: decimal point alignment, bit-by-bit calculation, and finally carry or abdicate. 2) Multiplication: first remove the decimal point from the decimal, then multiply the integer, and finally add up the digits of the decimal point. 3) Division: both the dividend and the divisor are multiplied by 10, so that the decimal point is shifted to the right by one place, and then it is divided by integer. 2. Fraction operation 1) General fraction: When the denominators of two fractions are different, they need to be replaced by the same denominator, that is, the general fraction. In general division, numerator and denominator can be multiplied by the same number at the same time. 2) Addition and subtraction: divide the scores equally, and then add and subtract according to the integer. 3) Multiplication: Multiply the numerator of two fractions, multiply the denominator, and then divide the fractions. 4) Division: Take the reciprocal of the divisor, turn it into multiplication, and then multiply it by the dividend. 3. Unit conversion Common unit conversions include length unit, weight unit and unit of volume. Among them, the conversion of length unit can adopt memory formula: long-distance knitting sweater and short-distance cycling. One mile equals 150, 169 bicycles. 4. Triangle includes equilateral triangle, isosceles triangle and equilateral triangle. The common properties of triangles are: 1) The sum of the internal angles of triangles is equal to 180 degrees. 2) The base angles of isosceles triangles are equal. 3) The length of the hypotenuse of a right triangle is equal to the square root of the sum of the squares of two right-angled sides. 4) All three angles of an equilateral triangle are 60 degrees, and the high lines are equally divided. 5. Rectangular and square Rectangular and square are two common rectangles. The circumference of a rectangle is twice the sum of its length and width, and the area is the product of its length and width. The circumference of a square is four times the length of its side, and its area is the square of its side.