The first unit division
1, divisor is a written calculation rule for dividing two digits:
(1) Look at the first two digits of the dividend from its high digits;
(2) If the first two digits are less than the divisor, it depends on the first three digits; In addition to the dividend, the business is written on that one;
(3) The remainder must be less than the divisor.
Divider is the division of two digits. Generally, the divisor is regarded as an integer close to it to try quotient. It should be reduced when the trial quotient is large, and increased when the trial quotient is small.
3. In the division formula with remainder, dividend = quotient divisor+remainder.
4. When three digits are divided by two digits, the quotient may be one digit or two digits.
Second unit angle
1. Extend one end of the line indefinitely and you will get a ray. Extend both ends of the line indefinitely and you will get a straight line. Line segments and rays are both parts of a straight line.
chart
similar
discrepancy
line segment
All straight men.
There are two endpoints, finite length (measurable)
ray
There is an endpoint, infinitely long.
straight line
No endpoint, infinite length.
2. You can draw countless straight lines after one o'clock, and only one straight line after two o'clock (two points determine a straight line).
3. In the connection between two points, the line segment is the shortest.
The length of the line segment connecting two points is called the distance between these two points.
Draw two rays from a point to form an angle. The angle is usually represented by the symbol "∞".
5. A corner has a vertex and two sides.
6. The angle is related to the size of the bifurcation on both sides, and has nothing to do with the length of the sides.
7. A protractor is a tool for measuring angles. Divide the semicircle into 180 equal parts (divided into 180 parts on average), and the angle of each part is 1 degree. "Degree" is the unit for measuring angles, which is represented by the symbol "0". For example, 1 is recorded as 1.
8. Angle measurement and angle drawing should be "point to point, line to the opposite side, and then look at the other side. 0 is inside the internal number and 0 is outside the external number.
9. The acute angle is less than 90; A right angle equals 90 degrees; Obtuse angle greater than 90 and less than180; Boxer180; Fillet 360.
1 fillet =2 right angle =4 right angle.
10, 1 hour, clockwise turns a big grid, diagonal 30; When the minute hand turns once, the right angle is 360.
Unit 3 Mixing Operation
1, in the mixed operation without brackets, if it only contains addition, subtraction or multiplication and division, it should be calculated from left to right; If you count addition, subtraction, multiplication and division, first calculate multiplication and division, then add and subtract.
2. In the mixed operation using parentheses, the inner side of parentheses should be calculated first.
Unit 4 Parallelism and Intersection
1. On the same plane, two disjoint straight lines are parallel to each other, one of which is parallel to the other. (In the same plane, two straight lines intersect if they are not parallel)
2. When drawing parallel lines, first put a triangular ruler, then put a ruler and translate the triangular ruler. (1) Draw a line; Second, a ruler; Three translations; Four lines)
When two straight lines intersect at right angles, they are perpendicular to each other, and one of them is perpendicular to the other. The intersection of these two straight lines is called vertical foot.
4. When drawing a vertical line, put a ruler first, then a triangular ruler, and translate the triangular ruler.
5. The vertical line segment between a point and a straight line is the shortest.
The length of a vertical line segment drawn from a point outside a straight line is called the distance from that point to this straight line.
6. All vertical line segments between two parallel lines are equal in length.
Unit 5 Looking for the Law
1. Two objects are arranged in a row at intervals.
If the objects at both ends are the same, the number of objects at both ends is more than that in the middle 1.
If the objects at both ends are different, then the number of two objects is the same.
Two objects are arranged in a circle one after another, and the number of two objects is the same.
2. Length of each interval х Several intervals = total length
Unit 7 Algorithm
Additive commutative law: a+b=b+a Addition Law: (a+b)+c=a+(b+c)
Multiplicative commutative law: aхb=bхa multiplicative associative law: (aхb)хc=aх(bхc)
Subtraction property: a-b-c=a-(b+c) (the continuous subtraction of two numbers equals the subtraction of the sum of these two numbers)
Nature of division: a÷b÷c=a÷(bхc) (continuous division by two numbers equals division by the sum of these two numbers).
Unit 8 Strategies for Solving Problems
Pay attention to one-to-one correspondence when solving problems with lists.
Unit 9 Statistics and Possibility
1. When sorting by segment, it depends on which segment the data is in, and no data can be lost.
When two people have equal chances to win, the rules of the game are fair.
Unit 10 Identification
1, 10 is ten thousand, 10 is one hundred thousand, 10 is one million, 10 is one million.
2 2. 10/010 million is one hundred million,1010 billion is one billion,1010 billion is ten billion,10100 billion is one hundred billion.
According to our country's counting habit, every four digits are counted from the right.
4. Several sequence tables
Several levels
……
Billion class
Ten thousand levels
Personal level
A few numbers
……
Billion bit
Billion bit
Billion bit
Billion bit
Ten million people
Millions.
One hundred thousand people
Hundred megabits
kilobit
The third number on the right
decade
unit
count
unit
……
billion
Ten billion
billion
a hundred million
ten million
million
one hundred thousand
ten thousand
a thousand
one hundred
ten
individual
5. The counting method with the ratio of 10 between every two adjacent counting units is called decimal counting method.
6. Reading, just add "10,000" or "100 million" at the end of each level;
The zero at the end of each level is not read, and other numbers have a zero or several zeros, all of which read only a "zero".
7, write the number, the number on the 10,000-level and the 100-million-level are written according to the method of personal level, and neither of them is enough to be supplemented by 0.
8. To rewrite numbers in units of "10,000" or "100 million", just remove the four zeros or eight zeros at the end and add the words "10,000" or "100 million".
9. Usually we use the method of "rounding" to approximate a number.
Look at the number with the highest mantissa. If it is 4 or less, the mantissa is discarded and all digits of the mantissa are rewritten as 0. If it is 5 or greater, add 1 to the previous digit, and then rewrite all digits of the mantissa to 0.
The 1 1 unit is counted by a counter.
The advantages of calculator are small size, fast operation speed and simple operation.
When looking for a rule with a counter, you should see clearly "change" and "unchanged". (What has changed, what has not changed, and how)
Supplementary concept: area of rectangle = length х width; The perimeter of the rectangle = (length+width) х2.
Area of square = side length х perimeter of side length square = side length х4
Length unit: kilometers → meters → decimeters → centimeters → millimeters.
Area unit: square meter → square decimeter → square centimeter
Mass unit: tons → kilograms → grams
Time unit: year → month → day → hour → minute → second.