1. Rounding method:
When taking decimal approximation, if the highest digit of mantissa is 4 or less, the mantissa is removed. If the highest digit of mantissa is 5 or more, the mantissa is rounded and "1" is input before it, which is called rounding method.
For example, the number 2. 1875 is accurate to one thousandth (third place after the decimal point). Since the fourth digit after the decimal point is 5, according to this rule, it should be carry 1, so the result is 2. 188.
Step 2:
One-step method is to add 1 to the last bit of the reserved part after removing the redundant figures. The approximation thus obtained is a residual approximation (i.e., greater than the exact value).
The characteristic of the binary system is that no matter how many decimal places, it is an integer plus 1, and the decimal is discarded. 4. One method of1is equal to 5, and one method of 4.9 is also equal to 5.
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.
The characteristic of truncation method is that no matter what the decimal places are, they are abandoned and only integer places are taken. For example, the truncation method of 4. 1 is equal to 4, and the truncation method of 4.9 is also equal to 4.