I. Mathematical terminology
A number is close to the exact number, and this number is called a divisor. Where the approximate number is rounded, it is where the approximate number is rounded, from the first number on the left that is not 0 to all the numbers until the exact number.
Second, significant figures.
Numbers that are close to the actual number, but not exactly the same, are called divisors. People often need to know the accuracy of approximate values. The accuracy of approximation is usually expressed in the following two ways:
1, expressed by rounding. Where the number is rounded off, it is said that the approximate number is accurate to which place.
2. There are two other methods: entering one and ending. Represented by significant figures. There is a rounding approximation, counting from the first non-zero on the left to the last number. All numbers are called significant numbers of this number. ?
Three or four operations
First of all, in general, the divisor is added and subtracted, and the known number with the lowest accuracy is accurate to which place, and the sum or difference can only be accurate to this place at most. Secondly, if the divisor is multiplied and divided, how many significant digits does a known number with the least significant digits have, and the product or quotient can only have the same significant digits at most.
Finally, the mixed operation of approximate numbers can be calculated step by step according to the operation order and the calculation rules of approximate numbers, but the result of intermediate operation is one more than the final result.
Characteristics and accuracy of approximate values
First, the characteristics:
More than half of the approximations are rounded to the smallest unit (not all), so it can be considered that the numbers above the smallest unit are credible and the numbers below the smallest unit are not. In the addition and subtraction of approximate numbers, the accuracy of the results must be evaluated according to the number with the lowest accuracy. In other words, the smallest unit of the lowest precision number is the precision that the result can achieve.
There is also a concept to evaluate the accuracy of approximate number, that is, effective number. The significant digits of the approximate number are the digits counted to the right from the first non-zero number on the rightmost side. The function of approximation in life is to facilitate calculation. Numbers that are close to the actual number, but not exactly the same, are called divisors.
Second, the accuracy:
A number is close to the exact number, and this number is called a divisor. The population of a city cannot be accurately calculated, but a rough figure can be given. For example, the urban population is 600 million, and 600 million is a rough figure. People often need to know the accuracy of approximate values. Determine the precision to which position by the conventional method, and take the approximate value according to the precision to which position.