Sum-difference problem
(sum+difference) ÷ 2 = large number (sum-difference) ÷ 2 = decimal.
And folding problems.
Sum ÷ (multiple- 1) = decimal × multiple = large number
Difference problem
Difference ÷ (multiple-1) = decimal× multiple = large number
Tree planting problem
1 The problem of planting trees on unclosed lines can be 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 ÷ plant spacing-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 = plant spacing × plant number = total length/plant number
(3) If no trees are planted at both ends of the non-closed line, then:
Number of plants = number of nodes-1 = total length ÷ plant spacing-1 total length = plant spacing × (number of plants+1)
Plant spacing = total length ÷ (number of plants+1)
The quantitative relationship of planting trees on the closed line is as follows
Number of plants = number of segments = total length/plant spacing = plant spacing × plant number = total length/plant number
The question of profit and loss
(Profit+Loss) ÷ Difference between two distributions = number of shares participating in distribution.
(Big profit-small profit) ÷ Difference between two distributions = number of shares participating in distribution.
(big loss-small loss) ÷ The difference between two distributions = the number of shares participating in the distribution.
encounter a problem
Meeting distance = speed and x 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 distance/speed difference
Speed difference = catching distance ÷ catching time
Tap water problem
Downstream velocity = still water velocity+flow velocity = still water velocity-flow velocity
Still water speed = (downstream speed+countercurrent speed) ÷2 Water flow speed = (downstream speed-countercurrent speed) ÷2
Time unit conversion
1 century = 100 1 year =1February (3 1 day) has:1\ 3 \ 5 \ 7 \ 8 \1.
Abortion (30 days) includes: 4\6\9\ 1 1, 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.
Calculation formula of perimeter, area and volume of mathematical geometry in primary schools
1, the perimeter of a rectangle = (length+width) ×2C=(a+b)×2 2, and the perimeter of a square = side length× 4c = 4a.
3. area of rectangle = length× width S=ab 4, area of square = side length× side length s = a.a = a.
5. Area of triangle = base × height ÷2S=ah÷2.
6. parallelogram area = bottom x height S=ah
7. trapezoidal area = (upper bottom+lower bottom) × height ÷ 2s = (a+b) h ÷ 2.
Definition theorem formula
Area of triangle = base × height ÷2. The formula S=a×h÷2.
Area of a square = side length × side length formula S = a× area of a rectangle = length× width formula S = A× B.
Area of parallelogram = base× height Formula S=a×h
Trapezoidal area = (upper bottom+lower bottom) × height ÷2 Formula S=(a+b)h÷2
Sum of internal angles: sum of internal angles of triangle = 180 degrees.
Cuboid volume = length× width× height formula: V=abh
Volume of cuboid (or cube) = bottom area × height formula: V=abh.
Volume of cube = side length × side length × side length formula: V=aaa.
Law of fractional addition and subtraction: Fractions with the same denominator are added and subtracted, only the numerator is added and subtracted, and the denominator remains the same. 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.