That is, numbers that are not 0 from the first place on the left to the last place (including 0, excluding the n power of 10 in scientific counting method) are called effective numbers. Simply put, removing all zeros in front of a number is a valid 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).

In 3. 109 * 105 (3. 109 multiplied by the fifth power of10), 3.109 are all valid numbers, and the fifth power of10 is not.

5200000000, all valid numbers.

0.0230, the first two zeros are not valid numbers, and the last 230 is valid numbers (the last two zeros are also counted).

1.20 has three significant figures.

1 100.024 has seven significant figures, and 3, such as 0. 123 has three significant figures (123).

0.00 123 (123) has three significant figures.

0. 1023 (1023) has four significant digits.

1230 (1230) has four significant figures.

The number of significant digits refers to the number from the first non-zero digit on the left to the last digit (including zero), regardless of the position of the decimal point. , 1, 1.0000 1 significant number is100000/significant number has 6 digits.

1.00 100 The significant number is 1 000 1 The significant number has 4 digits, 0,