The first volume of the fifth grade unit 1 summary of mathematical knowledge points: the preliminary understanding of negative numbers. Positive numbers and negative numbers are numbers with opposite meanings. 0 is neither positive nor negative, positive is greater than 0 and negative is less than 0. 0 is greater than any negative number. Unit 2: area calculation of polygon 1 Area of parallelogram = base × high letter formula: S=ah2. Area of triangle = base × height ÷2 letter formula: S=ah÷23. Trapezoidal area = (upper bottom+lower bottom) × height ÷2 letter formula: s = two identical triangles can form a parallelogram. 5. A parallelogram can be divided into two identical trapezoids; Two identical trapezoids can form a parallelogram. 6. The areas of triangles with equal bases and equal heights are equal; The area of a triangle is half that of a parallelogram with equal base and equal height. 7. Length units: millimeter (mm), centimeter (cm), decimeter (dm), meter (m) and kilometer (km). Propulsion rate:10101065438. Area unit: measure and calculate the land area, usually in hectares. Square land with side length 100 m and area 1 hectare (hm). Measure and calculate a large area of land, usually in square kilometers. A square piece of land with a side length of 1 000m and an area of1km2. 1 square kilometer (km) = 100000 square meter (m2) Area unit: square centimeter (cm2) square decimeter (dm2) square meter (m2) hectare (hm2) square kilometer (km2) Propulsion rate:1001. 8+0000 1000 10. unit of volume: milliliter (mL) liter (l) rate 1000 unit 3: the meaning and nature of decimal 1. The denominator is 10,100,65438. The second digit to the right of the decimal point is the percentile, and the counting unit is one percent (0.01); The third digit to the right of the decimal point is one thousandth, and the counting unit is one thousandth (0.001); The propulsion rate between every two adjacent counting units is 10. 4. Add 0 or remove 0 at the end of the decimal, and the size of the decimal remains the same, which is the essence of the decimal. According to the nature of decimals, decimals can usually be simplified by removing the 0 at the end of decimals. voidfunction(e，t){ for(varn = t . getelementsbytagname(" img ")，a=+newDate，i=[]，o = function(){ this . removeeventlistener & amp； & ampthis.removeEventListener("load "，o，！ 1)，i.push({img:this，time:+newDate})}，s = 0； s