What are the skills to change the proportion in the national examination preparation?

In the analysis of test data, the proportion of test sites is increasing, second only to the concept of "growth", and its importance is self-evident. Among the common specific gravity test sites, calculating the change of specific gravity is the most complicated and difficult to understand. Chinese public education experts found that many students' first reaction after seeing similar questions is to give up, but in fact, this kind of questions is very skilled, as long as they understand and remember, they can achieve "seconds kill".

I. What is "the change of calculated specific gravity"

You should know the concept of specific gravity. Specific gravity is the proportion of some values to the whole value, which is a percentage. As the name implies, calculating the change of specific gravity is to compare the difference between two specific gravity, and the difference between the two specific gravity must be a "percentage point". Frequently asked questions, such as:

In 2004, * * * accepted 353,800 patent applications, a year-on-year increase of 14.7%. In 2004, * * * granted 654380+090200 patents, up 4.4% year-on-year. 2007- National Examination-13 1

Question: Compared with 2003, the proportion of patent authorization in China in 2004 (authorization ratio = number of patent applications granted/number of patent applications accepted).

A. it increased by 5.3 percentage points. B. It dropped by 5.3 percentage points.

C. increased by 10.5 percentage points. D. Decrease by 10.5 percentage point.

This question is typical. Let's calculate the change of proportion, and the options are all percentage points. Among them, the increase or decrease of options can be understood as the proportion of the current period is higher or lower than the proportion of the base period.

I. Matters needing attention

We mentioned that the difference between the two ratios must be a "percentage point", but in fact, in some examination options, percentage points and percentage points are not strictly distinguished. When this happens, percentage points can be regarded as percentage points. Of course, if there are both percentages and percentage points in the option, choose percentage points!

Example: 20 1 1 year, the total number of migrant workers in China reached 252.78 million, an increase of10.55 million or 4.4% over the previous year. Migrant workers are still mainly engaged in manufacturing, construction and service industries, and the proportion of migrant workers engaged in construction industry has increased significantly. From the employment areas of migrant workers, there were1165.37 million migrant workers employed in the eastern region in 20 1 year, an increase of 3.24 million over the previous year; There are 44.38 million migrant workers working in the central region, an increase of 3.34 million over the previous year, with an increase of 8.1%; There were 4,265,438+500,000 migrant workers in the western region, an increase of 3.7 million or 9.6% over the previous year. 20 13- National Examination-13 1

Q: In 20 1 1 year, the proportion of migrant workers in the central region in the total number of migrant workers increased by about () compared with the previous year.

A.0.6% B.3.7%

C.6.2% D. 12.5%