Keeping two decimal places means keeping two decimal places, that is, there must be two decimal places. For example, 0. 1254, if the third place after the decimal point is more than 5, it becomes 0. 13, plus one; If it is 0. 123 1, and the third place after the decimal point is less than or equal to 4, then 0. 12 will be kept, because it is rounded, depending on which is the significant number.

In fact, this is just what we have been doing in the traditional sense, from junior high school to later, but in fact this error is also great. But our concept of daily study and life is completely acceptable. Many times, when we hand in forms and statistics, we will ask you to keep a few decimal places accordingly.

Just follow the rounding rule. However, there is a big difference between keeping two significant figures and keeping them to two decimal places. Effective number refers to the first number from left to right that is not 0 to the last number, and all the numbers in the middle are effective numbers of this number. Just like 0.0 12 is two significant numbers and 0.0 120 is three significant numbers.

Rounding rules for retaining significant digits:

1. When n significant bits are reserved, if the number of bits of n+ 1 is less than or equal to 4, it will be discarded.

2. When n significant bits are reserved, if n+ 1 bit ≥6, then n bits are 1.

3. When n significant bits are reserved, if n+ 1 bit is 5 and the following bits are 0, then if n bits are even, the following bits will be discarded, and if n bits are odd,1will be added; If the number of n+ 1 is 5, and there is any number that is not 0 after it, whether the number of n is odd or even, add 1.