2. We can never master the key mathematical skills of solving problems, treat each problem in isolation, and lack the ability to draw inferences from others; 3. When solving a problem, there are too many small mistakes, and the problem can never be completely solved;
4. The problem-solving efficiency is low, and a certain number of problems cannot be completed within the specified time, which is not suitable for the examination rhythm;
5. I haven't formed the habit of summarizing and summarizing, and I can't habitually summarize the knowledge points I have learned;
If these problems can't be solved well, in the polarization stage of junior high school, students may have a decline in their grades.
Primary school mathematics formula:
1, number of copies × number of copies = total number of copies, total number of copies/number of copies = number of copies, total number of copies/number of copies = number of copies.
2, 1 multiple × multiple = multiple, multiple1multiple = multiple, multiple = 1 multiple.
3, speed x time = distance, distance/speed = time, distance/time = speed.
4. Unit price × quantity = total price, total price/unit price = quantity, total price/quantity = unit price.
5, work efficiency x working hours = total workload, total workload ÷ work efficiency = working hours,
Total workload ÷ working time = working efficiency
6. Appendix+Appendix = sum, and-(one addend) = another addend.
7. Minus-Minus = difference, Minus-Minus = Minus, Minus+Minus = Minus
8. Factor × factor = product, product ÷ one factor = another factor.
9. Divider = quotient, dividend = divisor, quotient × divisor = dividend.
Calculation formula of perimeter, area and volume of mathematical geometry in primary schools
1, the perimeter of the rectangle = (length+width) ×2 C=(a+b)×2.
2. The circumference of a square = side length ×4 C=4a.
3. Area of rectangle = length× width S=ab
4. Square area = side length x side length s = a.a = a.
5. Area of triangle = base × height ÷2 S=ah÷2.
6. parallelogram area = bottom x height S=ah
7. trapezoidal area = (upper bottom+lower bottom) × height ÷ 2s = (a+b) h ÷ 2.
8. Diameter = Radius× 2D = 2r Radius = Diameter ÷2 r= d÷2
9. The circumference of a circle = π× diameter = π× radius× 2c = π d = 2π r.
10, area of circle = π× radius× radius.
Length unit conversion
1 km = 1 000m,1m = 10 decimeter.
1 decimeter = 10 cm, 1 m = 100 cm.
1 cm = 10/0mm
Area unit conversion
1 km2 = 100 hectare
1 ha = 1 10,000 m2
1 m2 = 100 square decimeter
1 square decimeter = 100 square centimeter
1 cm2 = 100 mm2
Volume (volume) unit conversion
1 m3 = 1000 cubic decimeter
1 cubic decimeter = 1000 cubic centimeter
1 cubic decimeter = 1 liter
1 cm3 = 1 ml
1 m3 = 1000 liter
Weight unit conversion
1 ton = 1000 kg
1 kg =1000g
1 kg = 1 kg
Rmb unit conversion
1 yuan = 10 angle.
1 angle = 10 point
1 yuan = 100 integral.
Time unit conversion
1 century = 100 1 year =65438+ February.
The big month (3 1 day) includes: 1, 3, 5, 7, 8,10,65438+February.
Abortion (30 days) includes: April, June, September,165438+1October.
February 28th in a normal year and February 29th in a leap year.
There are 365 days in a normal year and 366 days in a leap year.
1 day =24 hours, 1 hour =60 minutes.
1 minute =60 seconds, 1 hour =3600 seconds.
Tree planting problem
1. The problem of planting trees on unclosed lines can be mainly divided into the following three situations:
(1) If trees are planted at both ends of the non-closed line, then:
Number of plants = number of nodes+1 = total length-1.
Total length = plant spacing × (number of plants-1)
Plant spacing = total length ÷ (number of plants-1)
2 If you want to plant trees at one end of the unclosed line and not at the other end, then:
Number of plants = number of segments = total length ÷ plant spacing
Total length = plant spacing × number of plants
Plant spacing = total length/number of plants
(3) If no trees are planted at both ends of the non-closed line, then:
Number of plants = number of nodes-1 = total length-1.
Total length = plant spacing × (number of plants+1)
Plant spacing = total length ÷ (number of plants+1)
2. The quantitative relationship of planting trees on the closed line is as follows
Number of plants = number of segments = total length ÷ plant spacing
Total length = plant spacing × number of plants
Plant spacing = total length/number of plants
encounter a problem
Meeting distance = speed × meeting time
Meeting time = meeting distance/speed and
Speed Sum = Meeting Distance/Meeting Time
Catch up with the problem
Catch-up distance = speed difference× catch-up time
Catch-up time = catch-up distance ÷ speed difference
Speed difference = catching distance ÷ catching time
Tap water problem
Downstream velocity = still water velocity+current velocity
Countercurrent velocity = still water velocity-current velocity
Still water velocity = (downstream velocity+countercurrent velocity) ÷2
Water velocity = (downstream velocity-countercurrent velocity) ÷2
Concentration problem
Solute weight+solvent weight = solution weight.
The weight of solute/solution × 100% = concentration.
Solution weight × concentration = solute weight
Solute weight-concentration = solution weight.
Profit and discount problem
Profit = selling price-cost
Profit rate = profit/cost × 100% = (selling price/cost-1) × 100%.
Up and down amount = principal × up and down percentage
Discount = actual selling price ÷ original selling price× 1 00% (discount <1)
Interest = principal × interest rate× time
After-tax interest = principal × interest rate × time × (1-20%)