Total: 1. Understanding the number within 100 million 1. 1 (pieces), 10, 100, 100, 1 100 million are all units of counting. 2. What is the relationship between every two adjacent counting units? The propulsion rate of every two adjacent counting units is "10". 3. The method of finding the divisor is called "rounding". 4. Whether to "leave" or "enter" depends on whether the highest digit of the omitted mantissa part is less than 5 or more than 5.5. 1, 2, 3, 4, 5, 6 represents the number of objects. ..... are all natural numbers. The object is not represented by 0. 0 is also a natural number. 6. The smallest natural number is 0. Without the largest natural number, the number of natural numbers is infinite. 7. The forward rate between every two adjacent counting units is ten, which is called decimal counting method. 2. The measurement of angle is 1, such as flashlight, car light and sun. Connection: both rays and line segments are parts of a straight line, and line segments are limited parts of a straight line. The difference is that a straight line has no end, its length is infinite, and it extends to both sides. A ray has only one endpoint and its length is infinite, while a line segment has two endpoints and its length is limited. 4. Both straight lines and rays can extend indefinitely. A line segment can measure its length. The figure formed by two straight lines drawn from a point is called an angle. 6. Represented by the symbol "0". Divide the semicircle into 180 equal parts, and the angle of each part is 1 degree, and record it as 1.7. What is the relationship between acute angle, obtuse angle, right angle, right angle and rounded corner? Right angle =90 degrees, obtuse angle greater than right angle less than right angle, right angle = 180 degrees, fillet =360 degrees, acute angle less than 90 degrees.

Unit summary:

Names of numbers above 1 unit 1 100 million:

First, the reading method of hundreds of millions of miles: ○ 1 read first 1 10,000, and then read again 1. ○20000-level numbers should be read according to the pronunciation of each level, and then the word "10000" should be added at the end. ○3 No matter how many zeros are at the end of each level, don't read them; There are one or several zeros in the middle, all of which are read-only ones. Second, the writing method of the number within 100 million: ○ 1 Write 10,000 levels first, and then write one level. ○2 Which number goes to the next unit?

No, just write 0 in one place. zero

Be sure to grade before reading or writing. Third, the method of comparing the size of numbers: ○ 1 When the number of digits is different, the number with more digits is larger. ○ When the two digits are the same, starting from the highest digit, the number on the highest digit is larger, and this number is larger; If the numbers on the highest bit are the same, compare the numbers on the next bit until the sizes are compared.

Fourth, the method of rewriting an integer into a number with "ten thousand" as the unit; Omit the four zeros after ten thousand digits and replace them with a word "ten thousand".

5. Method of rounding to find the divisor: Finding the divisor of a number mainly depends on the mantissa it omits. If the highest digit of the omitted mantissa is 0, 1, 2, 3, 4, we will discard all mantissas and rewrite them as "0"; If the highest digit of the mantissa is omitted, it is 5, 6 and 7.

6. The key to finding the divisor by "rounding" method: finding the highest digit of mantissa. If the mantissa after ten thousand digits is omitted, it depends on thousands; If you omit the mantissa after thousands, look at hundreds; If the mantissa after 100 digits is omitted, look at 10 digits.

7. The numbers 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9 representing the number of objects are all natural numbers, and 0 is the smallest natural number. There is no maximum natural number, and the number of natural numbers is infinite.

Eight, the ratio between every two adjacent counting units is ten. This counting method is called decimal counting method. Nine, the reading method of numbers above 100 million is the same as that of numbers below 100 million: in the first grade, read from the highest place, read from the first level to the next level, read according to the reading method of the first level when reading the billion level, and then add the word "100 million" at the back.

The number above 100 million is written in the same way as the number below 100 million: first grade, starting from the highest place, writing down one level at a time, and writing at each level is the same. 1 1. The key to reading and writing is "grading first".

12. rewrite the integer: directly omit the eight zeros after the billion bits and add a word "billion". 13. If it is not an integer, use rounding method to omit the mantissa after 100 million digits and rewrite it: first grade and then "round" the highest mantissa, and use "?" Write numbers, don't forget to write the word "billion".

Fourteen, each file on the abacus represents a number. Before counting, make sure that a file is a number with ten, one hundred and one thousand digits to the left. The upper bead of each gear represents 5, and the lower bead represents 1. Fifteen, the function of electronic calculator operation keys.

Symbol name function on /C on key to open or erase input content off key to close CE erase key to erase only the content just entered last time.

Measurement of the second unit angle

First, the connection and difference between straight lines, rays and line segments

The number of endpoints whose related areas are all straight is expanded.

Nothing in a straight line can extend to both ends indefinitely.

The ray 1 can extend to one end indefinitely.

Line segment 2 cannot extend to one end at any length.

Second, you can draw countless rays from one point, countless straight lines after one point, and only one straight line after two points.

3. The protractor consists of a center point, a zero scale line, an inner scale and an outer scale. When measuring the angle, pay attention to: (1) The center point of the protractor coincides with the vertex of the angle. (2) Make the internal scale of the protractor coincide with one side of the angle. (3) Where the other side of the corner points depends on the inner circle (outer circle).

Fourth, the size of the angle has nothing to do with the length of both sides of the angle, but with the size of the bifurcation on both sides. The bigger the bifurcation on both sides, the greater the angle.

5. An angle less than 900 is called an acute angle, and an angle greater than 900 is less than 1800.

This angle is called obtuse angle.

6. 1 Boxer 1800

=2 right angle

1 fillet =3600

= 2 right angle = 4 right angle

Seven, acute angle