★ Fast calculation skills 1: estimation method
There is no doubt that "estimation method" is the first fast calculation method in data analysis, and whether it can be estimated first must be considered before all calculations are made. The so-called estimation is a fast calculation method of rough estimation under the condition that the accuracy requirement is not too high, which is generally used in the case of large difference in options or comparison data. There are many ways to estimate, which require candidates to train and master more in actual combat. The premise of estimation is that the difference between the options or the numbers to be compared must be large, and the size of this difference determines the accuracy requirements of "estimation". There are three main situations:
1. Majority addition: Truncated according to the option, and then added.
2. Most addition comparisons: This part of the question type is relatively simple, only column comparisons are needed, and no real addition is needed.
3. Average: replace and exclude with options; First, according to the data given by the material, eliminate unreasonable options. According to the customary principle, the remaining options are replaced and excluded.
★ Quick calculation skill 2: Direct division
? Direct segmentation? Refers to the calculation of long data division operation, through? Direct segmentation? A method of obtaining several digits of the quotient (usually the first digit or the first two digits), so as to choose a fast calculation method of the correct answer.
1. Directly ranked first:
The divisor (numerator) remains unchanged, and the divisor (denominator) keeps two digits (rounding) for division and division by the first digit.
2. Divided by two digits:
Divider (numerator) remains unchanged, divisor (denominator) keeps three digits (rounding) for division, and the first two digits are divided.
3. Divide directly by multiple numbers:
The divisor (numerator) remains the same, and the divisor (denominator) is one bit more than the number of digits to be calculated by the option (rounding), and the first few digits are divided.
★ Quick calculation skill 3: Formula method
1. Divide the growth rate by multiplication:
Find the base period, (r? 5%)。 The present value is a and the growth rate is R.
Precautions: ① Scope of use, it is recommended to use it within the scope, and never use it outside the scope;
(2) In the process of division into multiplication, the sign changes;
3 is not one? (1-r) to calculate A-A? r，A？ R rough estimate;
(4) Only one option is close to the calculated answer, so you can choose it directly regardless of the size;
⑤ There are two options close to the calculated answer, so choose the larger option.
2. Interval growth rate:
Interval growth rate R=r 1+r2+r 1? r2 .
The growth rate between the first and second phases is r 1, the growth rate between the second and third phases is r2, and the growth rate between the first and third phases is R.
★ Fast Calculation Skill 4: Scaling Method
"Scaling method" refers to a fast calculation method that can boldly "scale" (enlarge) or "shrink" (shrink) the intermediate result in the comparison and calculation of numbers, so as to quickly get the size relationship of the numbers to be compared.
Key points:
If A & gtB& gt；; 0, while C>D>0 has:
1.a+C & gt； B+D
2.A-D & gt； B-C
3. A C>B D
4.a/D & gt； B/C
These four relations, that is, the four mathematical inequality relations described in the above four examples, are very simple and basic inequality relations that we often need to use in doing problems, but they are mathematical relations that candidates easily ignore or miss in the examination room, and their essence can be explained by "scale method".
★ Fast calculation skill 5: Score comparison
1. Score attribute
For two fractions with the same denominator, the fraction with larger numerator is larger;
For two fractions with the same numerator, the fraction with the larger denominator is smaller.
Inference: When comparing two fractions, the fraction with relatively large numerator and relatively small denominator is larger.
2. Direct division
For scores of the same order of magnitude, the higher the first digit of the quotient, the greater the score.
Divide each number by the first place. If you can judge, choose the answer. If you can't judge, divide it by the second place.