1, rounding method, when taking decimal approximation, if the highest digit of mantissa is 4 or less, the mantissa will be removed; if the highest digit of mantissa is 5 or more, the mantissa will be removed and1will be entered before it;

2. The decimal method refers to adding 1 to the last digit of the reserved part after removing the redundant digits, and the approximation is the residual approximation, that is, it is greater than the accurate value;

3. Truncation refers to the commonly used mathematical value-taking method of removing the decimal part of a number and taking its integer part. Its value is approximate, that is, less than the exact value. Truncation method is suitable for life, also called truncation principle.

effective digit

Numbers that are close to the actual number, but not exactly the same, are called divisors.

People often need to know the accuracy of approximate values. The accuracy of approximation is usually expressed in the following two ways:

1, expressed by rounding. Where the number is rounded off, it is said that the approximate number is accurate to which place.

2. There are two other methods: entering one and ending. Represented by significant figures. There is a rounding approximation, counting from the first non-zero on the left to the last number. All numbers are called significant numbers of this number.