First, the application of significant number method in addition and subtraction.
According to the significant digits of the calculation result, it is judged that several significant digits need to be taken to participate in the operation, that is, the calculation bit and the observation bit are determined (generally, three significant digits are reserved in the calculation result).
1. Determines whether the magnitude of data involved in the operation is consistent.
2. Whether it is necessary to carry or abdicate the estimated results.
3. Determine the calculation bit and observation bit
For example: 2 15.38+ 184.25, the calculation bits are 2 15 and 184, and the observation bits are 3 and 2.
(1) principle of addition: (calculation results generally retain three significant figures)
1. Observation bit addition
2. The sum of observation positions is ≥5, and
3. Observation bit addition ≥ 15 and
4. and so on.
(2) Subtraction principle: (Generally, three significant figures are reserved in the calculation result)
1. When the observed bit difference is less than or equal to 5, directly subtract the calculated bit; For example: 456.3-345. 1≈456-345
2. Observe the phase difference >; 5 o'clock, one in and one out: observe the number with large digits and add1to its calculated digits; Observe the number with small bits and calculate that the bits are unchanged. For example: 456.9-345.2≈457-345
Second, the application of significant number method in multiplication:
According to the formula, the first two significant digits are calculated digits, and the third significant digit is observed digits, regardless of decimal point.
1. When all the third significant digits are 0/ 1/2, directly take the first two significant digits for operation, that is, all the third significant digits are rounded off; For example: 48./kloc-0 /×18.2 ≈ 48×18.
2. When all the third significant digits are 8/9, all the third significant digits are input1; For example: 48.8× 18.9≈49× 19.
3. When the third significant figure is other cases, one in and one out: the data of the first three significant figures are small, and the observed figures are rounded off; For the data with large first three significant figures, observe the opposite trade-offs. For example: 48.3× 18.9≈48× 19.
Third, the application:
1. According to the data released by the National Bureau of Statistics, the added value of the primary industry in 20 12 was 3,547.7 billion yuan, including agriculture, forestry, animal husbandry and fishery services, with a real increase of 4.2% over the previous year.
Q: According to the growth rate of 20 12, how many billion yuan can the primary industry achieve in 20 13?
a . 36967 b . 37605 c . 405 14d . 50377
China public opinion analysis: according to the final value = initial value× (1+average annual growth rate), the formula of this question is 35,477× (1+4.2%) ≈ 36×1.0, which is the closest to option A..
2. After 1980, there were125.28 million new generation migrant workers, accounting for 46.6% of the total number of migrant workers and 65.5% of the rural employed labor force born after1980. Among the new generation of migrant workers, the education level below junior high school only accounts for 6. 1%, junior high school accounts for 60.6%, senior high school accounts for 20.5%, and college education or above accounts for 12.8%.
Q: Among the new generation of migrant workers in 20 13, how many have junior high school education or above?
a . 759 1 b . 9433 c . 1 1764d . 16 136
Analysis of Chinese workers: According to the new generation125.28 million migrant workers, the education level below junior high school accounts for 6. 1%, and the formula of this question is12528× (1-6.1%) =1.
The above is the effective number method of fast estimation skills introduced by Chinese public education. I hope you can accurately grasp and apply it to the problem of data analysis!