A divisor is a number that is close to an exact number. Among them, the exact number is the most original data of this number, and it is expressed without any simplification, simplification and rounding. Approximation is a number that is not much different from the original data by rounding, entering a method or truncating.

Addition and subtraction of divisor

In general, the approximate value is added and subtracted, and the known number with the lowest accuracy is accurate to which position, and the sum or difference can only be accurate to this position at most. For example, a classmate weighed 30.4 kilograms in the previous year, and his weight increased in the second year.

3. 18kg。 Add up these two approximate figures when calculating the weight in the second year. Because 30. 4 is only accurate to the tenth place, lower than 3. 18 (accurate to hundreds), and the sum can only be accurate to the tenth place at most. In order to easily see the reliability of the calculation results, we added a "?" At the end of each addend in the vertical position. A used to represent truncated numbers.