Knowledge points of mathematics "angle measurement" in the first volume of the fourth grade of People's Education Press
1. Line, light, angle
Straight line: a line that extends infinitely to both ends and has no end.
Ray: it can be like a line extending in one direction, and the ray has an endpoint.
Line segment: a line that cannot be extended. A line segment has two endpoints.
Angle:
A figure composed of two rays with a common endpoint is called an angle.
This common endpoint is called the vertex of the angle, and these two rays are called the two sides of the angle.
2. The connection and difference between straight lines, rays and line segments.
1) Both lines and rays can extend indefinitely, so the length cannot be measured.
2) The length of the line segment can be measured.
3) A line segment has two endpoints, a straight line has no endpoint, and a ray has only one endpoint.
3. The characteristics of angle
A corner has a vertex and two sides.
Knowledge points of mathematics "hectares and square kilometers" in the first volume of the fourth grade of People's Education Edition
1. The area units that have been learned are square centimeter (cm2), square decimeter (dm2), square meter (m2), hectare and square kilometer (km2).
2.( 1) A square with a side length of 1cm and an area of 1cm.
(2) A square with a side length of 1 decimeter and an area of 1 square decimeter.
(3) A square with a side length of 1m and an area of 1m2.
(4) Square with side length 100 m and area 1 hectare. 1 ha = 1 10,000 m2
The area of land can be measured in hectares.
For example, the Bird's Nest covers an area of about 1 hectare. The area surrounded by the runway 400 is about 1 hectare.
(5) A square with a side length of 1000m and an area of 1 km2.
1 km2 = 100 hectares =1100 million m2.
China has a land area of about 9.6 million square kilometers.
3. Conversion between area units:
(1) First, remember the progress between them:
1 km2 = 100 hectares =1100 million m2.
1 ha = 1 10,000 m2
1 m2 = 100 square decimeter
1 square decimeter = 100 square centimeter
1 m2 = 10000 cm2
(2) conversion method:
○ 1 To convert a high-level unit into a low-level unit, it is necessary to use multiplication to calculate, just multiply the number in front of the high-level unit by the ratio between the two units. (that is, the height, the rate of progress, the decimal point moves to the right, and you can see the rate of progress by moving a few places. )
2 To aggregate low-level units into high-level units, it is necessary to calculate by division, as long as the number in front of the low-level unit is divided by the ratio between two units. (that is, reduce the level, divide by the forward speed, move the decimal point to the left, move a few positions, and see the forward speed. )
A. To convert hectares into square meters, just write four zeros directly after the data in front of hectares.
B, to convert square meters into hectares, just remove four zeros from the data in front of the square meters.
C. To convert a square kilometer into a hectare, just write two zeros directly after the data in front of the square kilometer.
D, convert a square kilometer into a square meter, just add six zeros directly after the data in front of the square kilometer.
E, to convert a square meter into a square kilometer, just remove six zeros from the data in front of the square meter.
4, fill in the legal provisions of the area unit:
(1) Land area, province (including municipality directly under the central government) area, provincial capital city area, state (city) area, county, township area, village committee and village area, generally taking "square kilometers" as the unit.
(2) Parks, colleges (schools), stadiums (gymnasiums), etc. , generally in "hectares" as the unit.
(3) Housing (building) area, classroom area, campus greening area, etc. , are generally measured in square meters.
Knowledge points of Understanding Large Numbers, the first volume of fourth-grade mathematics published by People's Education Press.
1.1010,000 is 100,000,1010,000 is 1 million,101 million is 10 million,1010 million is 100 million.
The advance rate between every two adjacent counting units is "10". This counting method is called decimal counting method.
Special attention: the difference between counting units and numbers.
2. When using numbers to represent numbers, these counting units should be arranged in a certain order, and their positions are called numbers.
3. Number of digits: A number contains several digits, that is, several digits. For example, 652 100 is a six-digit number.
According to our country's counting habit, every four digits are counted from the right.
5. How to pronounce hundreds of millions or more:
(1) Grading first, starting from high reading. Read level 100 million, then level 10,000, and finally level 1.
(2) Billions should be read according to the pronunciation of billions, and then the word "billion" should be added at the end. Ten thousand series should be read according to the reading method of ten thousand series, and then the word "ten thousand" should be added after it.
No matter how many zeros there are at the end of each level, don't read them. Other numbers have a "0" or several "0" in succession, all of which are read only.
6, hundreds of millions of words:
(1) Write from bits, first write 100 million levels, then write 10,000 levels, and finally write one level.
(2) If there is no unit, just write 0 on the number.
7, compare the size of the quantity:
The two numbers are different, the one with more numbers is bigger and the one with fewer numbers is smaller.
(2) Two numbers with the same number of digits, starting from the number of digits, the number with the largest number of digits is larger. If the numbers on the numbers are the same, compare the numbers on the next number until the size is compared.
8. Number of rewrites:
Rewrite it into a number in the unit of "10000" or "10000000". Draw a grading line first, divide the integer 10 thousand or integer 100 thousand into four levels, then omit four zeros from each level and replace them with the word "100 thousand"
Summarize the relevant articles about the knowledge points of fourth grade mathematics;
★ Summarize the knowledge points of the first volume of mathematics in the fourth grade of primary school.
★ Summary of Mathematics Knowledge Points in Grade Four
★ Summary of Mathematics Learning Knowledge in Grade Four
★ Summary of knowledge points in the first volume of fourth grade mathematics
★ Summarize the knowledge points of the fourth grade mathematical triangle.
★ Summary of knowledge points in the fourth grade of the first volume of mathematics
★ Guidance and summary of mathematics learning methods in the fourth grade of primary school
★ Summarize the knowledge points of mathematics in the second volume of the fourth grade.
★ Summarize the knowledge points of mathematics in the second volume of Grade Four (2)
★ Guidance of mathematics learning methods in the fourth grade of primary school