What is the specific meaning of decimal

What is the specific meaning of decimal

The meaning of decimal
Decimals are composed of integral parts, decimal parts and decimal points. When measuring objects, we often get numbers that are not integers. The ancients invented decimals to supplement integers. Decimals are a special form of decimal fractions. Denominators are 10, 100, 1000 All fractions can be expressed as decimals, except infinite non circulating decimals. Irrational numbers are infinite non circulating decimals. According to the decimal value principle, the decimal fraction is written as an integer without denominator. Such numbers are called decimals. The dots in decimals are called decimal points, It is the dividing mark between the integer part and the decimal part of a decimal. The part on the left side of the decimal point is the integer part, and the part on the right side of the decimal point is the decimal part. A decimal whose integer part is zero is called a pure decimal, and a decimal whose integer part is not zero is called a decimal. For example, 0.3 is a pure decimal, and 3.1 is a decimal
To understand the meaning of a decimal, we can start with the meaning of a fraction. The meaning of a fraction can be explained from the sub division and synthesis activities. When a whole (the reference quantity) is divided equally, the quantity that gathers part of it is called "component", and "fraction" is used to express or record the "component". For example, 2 / 5 means that an integer is divided into five equal parts, When the whole is divided into ten equal parts, one hundred equal parts, one thousand equal parts For example, 1 / 10 is recorded as 0.1, 2 / 100 as 0.02, 5 / 1000 as 0.005 The decimal point is used to separate the part of an integer from the part of a decimal that cannot form an integer. If the integer is not zero, it is called a decimal. If it is zero, it is called a pure decimal. Therefore, the meaning of a decimal is a part of the meaning of a fraction

How to keep valid numbers (for example)
If it is 0.12004, keep 3 significant numbers, what are the significant numbers?

The three significant digits of 0.120 are 1, 2 and 0 respectively. The rounding rules of 1. When n significant digits are reserved, if the N + 1 digit is ≤ 4, it will be rounded off. 2. When n significant digits are reserved, if the N + 1 digit is ≥ 6, the n-th digit will be rounded to 1.3. When n significant digits are reserved, if the N + 1 digit is 5 and the following digit is 0

What is to keep one decimal place, what is to take 0.1, and what is to keep one significant digit,

First, to keep one decimal place is to keep one decimal place after the integer, such as 0.1, 0.2, 0.3, 0.4, etc. if it exceeds, it will be rounded off, such as 0.13 to keep one decimal place is 0.1; 0.16 to keep one decimal place is 0.2