Scientific counting method to retain significant numbers to be rounded?

Scientific counting method to retain significant numbers to be rounded?

There are many concepts about scientific counting, approximate number and significant number, and students often encounter difficulties in learning. The following is an analysis of the mistakes made by students in solving problems, for your reference
1、 The concept is not clear
Example 1 the number and accuracy of significant digits of approximate number 0.03020 are ()
A. Four, accurate to 100000 B. three, accurate to 100000
C. Three, accurate to ten thousand D. four, accurate to ten thousand D
There are three significant digits in the wrong solution, that is, 3 in the percentile, 0 in the thousandth, and 2 in the ten thousandth, that is, there are three significant digits; 2 in the ten thousandth, that is, there are ten thousandth
Analyze an approximate number, from the first non-zero number from the left to the exact digit, all numbers are called the significant digits of the approximate number; an approximate number, which digit is rounded to, is the exact digit of the approximate number, that is, 0.03020 is accurate to 100000
Positive solution a
2、 Neglecting the restrictive conditions in scientific counting
In example 2, the approximate value of 40230 is taken by the rounding method. If two significant numbers are retained, it is expressed by the scientific counting method as____________ .
Wrong solution 40 ×
In the analysis of the wrong solution, two significant numbers are reserved, but there is a mistake in the representation of the number in the scientific counting method. This is because the form of the scientific counting method "×" must meet the condition 110. The positive solution 402304.0 ×
3、 Does not represent an approximation
Example 3 uses the rounding method to take the approximate number in brackets: 80642 (keep 3 significant numbers)
Wrong solution 80642 80600
If we write the result as 80600, we can't see which are the retained significant numbers. For example, this kind of "large number", we can use the scientific counting method to express the approximate number, and the significant number of the number before the multiplier sign is the significant number of this approximate number
The positive solution is 806428.06 ×
4、 Leave out the zeros at the end of the decimal
In example 4, the approximate value of 1.2045 to the hundredth is used to get ()
A.1.20 B.1.2 C.1.21 D.1.205
Wrong choice of B. or C
If the analysis is accurate to the hundredth, it means that two decimal places should be reserved, and the 0 on the hundredth cannot be removed, so B and D are wrong; if two decimal places are reserved, the third decimal place should be rounded, and the fourth decimal place 5 cannot be entered into the thousandth place,