Rounding is an accurate counting reservation method, 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 half of the last order of magnitude: if there is a probability of 0 ~ 9, the error sum of this method is the smallest for a large number of reserved data. This is why we use this method as the basic booking method.

example

For example, π is rounded off, leaving 3. 14. But sometimes you can use "one-in method" and "one-out method" instead of rounding. The rounded fourth house is 1, 2, 3, 4 and the fifth house is: 5, 6, 7, 8, 9. For example, 288 students have a spring outing, and 45 people have a bus, which is 6.4 buses. However, you must get into a bus to avoid letting more people out and fewer cars. Because the number of cars cannot be decimal, seven buses are needed.