The integer 1 can be divided into 10, 100 and 1000, which can be expressed in decimals.
One decimal place indicates a few tenths, two decimal places indicate a few percent, and three decimal places indicate a few thousandths.
Decimal system consists of integer part, decimal part and decimal part. The point in the number is called the decimal point, the number to the left of the decimal point is called the integer part, and the number to the right of the decimal point is called the decimal part.
In decimals, the series between every two adjacent counting units is 10. The propulsion rate between the tenth of the highest decimal unit in the decimal part and the first of the lowest decimal unit in the integer part is also 10.
2. Classification of decimals
Pure decimals: Decimals with zero integer parts are called pure decimals. For example, 0.25 and 0.368 are pure decimals.
With decimals: decimals whose integer part is not zero are called with decimals. For example, 3.25 and 5.26 are all decimals.
Finite decimals: The digits in the decimal part are finite decimals, which are called finite decimals. For example, 4 1.7, 25.3 and 0.23 are all finite decimals.
Infinite decimal: The digits in the decimal part are infinite decimal, which is called infinite decimal. For example: 4.333. 14 15926.
Infinite acyclic decimal: the decimal part of a number with irregular arrangement and unlimited digits. Such decimals are called infinite cyclic decimals. For example:
Cyclic decimal: the decimal part of a number, in which one or several numbers appear repeatedly in turn, is called cyclic decimal. For example: 3.5550.012.109438+009.
The decimal part of cyclic decimal is called the cyclic part of cyclic decimal. For example, the cycle node of 3.99 is 9, and the cycle node of 0.5454 is 54.
Pure cyclic decimal: the cyclic segment starts from the first digit of the decimal part, which is called pure cyclic decimal. For example: 3.1110.5656
Mixed cycle decimal: the cycle section does not start from the first digit of the decimal part. This is called mixed cyclic decimal. 3. 12220.03333
When writing a cyclic decimal, for simplicity, the cyclic part of the decimal only needs one cyclic segment, and a dot is added to the first and last digits of this cyclic segment. If there is only one number in the circle, just click a point on it. For example: 3.777 short form 0.5302302 short form.
Summary of Mathematical Decimal Knowledge Points Part II Unit 1 Angle and Decimal
Unit knowledge point
1, combined with the specific situation of shopping, initially understand the meaning of decimals, and can recognize, read and write simple decimals.
2. By exploring the process of how to compare decimal sizes, we can compare decimal sizes according to the shopping situation.
3, can calculate the addition and subtraction of a decimal, and can solve some related simple problems. (closely related to elements, angles and minutes)
4. Be able to use decimals to express some things in daily life and communicate.
Buy stationery
1, initially understand the specific meaning of decimal system, understand the relationship between decimal system and the unit of actual quantity it represents, and know, read and write simple decimal system.
2. Compare these decimals with the numbers they have learned before, and let them find that all decimals have decimal points.
3. Pay attention to the special position of 0 in decimal.
Shop around; Shopping around
1. Master the method of comparing decimal sizes flexibly and compare decimal sizes independently.
2. Cultivate the awareness of estimation.
3. The consecutive zeros at the end of the decimal part can be removed.
Buy a book.
1, in the process of various algorithms, teachers should guide students to observe the * * * situation of different algorithms, that is, the numbers of the same unit (digits) can be added.
2. Master vertical decimal addition and subtraction.
3. Master the vertical format (decimal point alignment).
Send a book
1, using decimal knowledge to solve practical problems in life.
2. Correctly handle the arithmetic problems that need to be carried or abdicated in the process of decimal addition and subtraction.
3, flexible use of estimation knowledge, and can explain the estimation process.