There are two main points: (1) accurate to one digit, that is, keep an integer and look at ten digits; Accurate to the tenth place means to keep one decimal place, depending on the percentile; Accurate to 1% means to keep two decimal places, depending on one thousandth, and so on. For example, to which place is accurate means to keep a few decimal places, depending on the latter one. When approximating, the 0 at the end of the small tree cannot be removed. For example, 1.0 is equal to 1, but their accuracy is different.