Effective Numbers From the first non-zero number to the left of a number to the last number, all numbers are effective numbers of this number. For example: 0.0 109, the first two zeros are not significant numbers, and the following 109 is significant numbers (note that the middle zeros are also counted). Similarly, if 0.0 109 retains two decimal places, it is 0.0 1.

Second, the location is different:

Decimal system is a special form of real number. All fractions can be expressed as decimals, and the points in decimals are called decimal points, which are the dividing lines between the integer part and the decimal part of a decimal. According to the real number 10. 1 1, the number of decimal places is 1 1. The valid numbers are different. The significant digits are counted from the leftmost nonzero digit of the real number, and the two significant digits of the real number 10. 1 1 are 10.

Three. Different forms of booking:

1.0023, with two decimal places, it is 1.00, with two decimal places. If two significant digits are reserved, it is 1.0, and the first digit that is not 0 starts to take two digits. For example: 0.0 123, if two decimal places are reserved, it will be 0.0 1, and the third decimal place will be rounded off. When two significant digits are reserved, they can only be raised by power, so it should be 1.2× 10 (-2), which means that -2 in brackets is raised to -2.

Baidu Encyclopedia-Effective Numbers

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