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How to explain rounding in primary school mathematics?
Rounding depends on the exact number of digits, and the exact number of digits depends on whether the previous digit is full of 5 (that is, greater than or equal to 5). If it is full of 5, it will advance one place; if it is less than 5 (that is, less than 5), it will be discarded, and the following number will become 0.

Rounding is basically 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 probably why this method is used as the basic reservation method.

Homotypic algorithm

From the statistical point of view, "four families, six families and 50% pairs" is more scientific than "rounding", which makes the rounding result bigger, smaller and more uniform. Instead of entering it every Friday like rounding, the result is biased towards large numbers.

For example:1.15+1.25+1.35+1.45 = 5.2. If one decimal place is rounded, the calculation is as follows:

1.2+ 1.3+ 1.4+ 1.5=5.4

According to the calculation of "four houses in six and fifty pairs",1.2+1.2+1.4+0.4 = 5.2, the rounding result can better reflect the actual result.

In C#, the result of int. Tostring ("F2") is calculated according to the rule of four families, and six families are divided into 50% pairs. Rounding in other calculation software, such as Matlab, is mostly handled in this way.

Above content reference: Baidu Encyclopedia-Rounding