1, rounding
Rounding is a method of counting degrees, which is essentially the same as other methods. But the special point is that the difference between the reserved part and the actual value cannot exceed one-half order of magnitude after rounding: if there is a probability of 0 ~ 9, the total error of this retention method is relatively small for a large number of reserved data. This is why we use this method as the basic booking method.
2, into the law
The binary method is to add 1 to a number after removing the redundant parts and keeping some comparisons. The approximation thus obtained is a residual approximation (i.e., greater than the exact value).
In our real life, rounding is not always possible, and sometimes rounding is used (that is, as long as the omitted digits are greater than zero, one digit must be entered). In order to make the results closer to the objective reality or make the results meaningful.
3. Tailing method
Truncation is a commonly used mathematical method, which removes the decimal part of a number and takes its integer part, and its value is approximate (less than the exact value), which is often used in life. Also known as the tail cutting principle.
4, quantity unit estimation method
Use real-life objects to perceive units of quantity and actually experience the size of data.
"Rounding" method:
Looks like one more digit than the reserved number. The number of digits in this number is "5" or greater. If the number of digits on this digit is "4" or less, discard it, such as 6.56, and keep one decimal place, which is 6.6. And 6.54, one decimal place is 6.5.
When taking decimal divisor, if the highest digit of mantissa is less than 4, the mantissa shall be removed; If the most significant digit of the mantissa is 5 or more, the mantissa is discarded and "1" is input in its previous digit. This method of taking the divisor is called rounding.
"Nine Chapters Arithmetic" also adopts the method of "rounding". When using the proportional method to find the vehicles that should be dispatched in each county, because the vehicles are integers, the calculation results are rounded off.