Guangxi civil servant exam preparation: solving problems skillfully
Mathematical operation has always been a compulsory question in Guangxi civil service examination, and it is also a headache for many candidates. It takes a lot of time to score such questions, but it may not be possible. Coupled with the tight test time, many candidates can only give up in the face of mathematical operations. Candidates don't really understand the questioner's intention and the purpose of the exam. Mathematical operation examines the examinee's thinking, not the speed of calculation. This part of mathematical operation must not be abandoned. Today, Chinese public education experts introduce the idea of divisibility to you, so that you don't have to worry about mathematical operations anymore!
The idea of divisibility refers to the sharp weapon for solving problems by using the divisibility of numbers to quickly judge options and get answers. In the civil service exam, because most of the topics are adapted from our real life, such as raising pigs and planting trees, these things must be described by integers. In this kind of problems, the idea of divisibility can often be used, which can greatly reduce the time for doing the problems. The following Chinese public education experts use several examples to discuss how to solve problems by divisible method.
Example1:The distance between A and B is 2 10 km. Two cars, A and B, start from A and B at the same time and travel back and forth continuously. The speed of car A from A is 90km/h, and the speed of car B from B is120km/h.. After starting from a for the second time, ask a car to meet b car. How many kilometers has the B car traveled?
A.560 km B.600 km C.620 km D.630 km
According to the conclusion of the encounter problem in the travel problem, the distance between the two places is 2 10 km, and the speed sum of the two cars is 90+ 120 = 2 10 km, so the first encounter time of the two cars is one hour. According to the conclusion, the future meeting must be a whole hour, no matter how many times. The speed of car B is 120km/h, so the total distance must be divisible by 120, so the locking answer is B.
Example 2: A mobile phone manufacturer makes a profit of 10% from a mobile phone he just sold, but if he buys it at a price lower than the original purchase price of 10% and sells it at a profit price of 20%, the price will decrease 25 yuan. How much does this mobile phone cost?
1250， 1375， 1550， 1665
According to the formula, selling price = buying price ×( 1+ profit rate). The first profit rate is 10%, and the formula brought in is selling price = purchase price (1+ 10%), so the selling price must be divisible by 1 1, and only B meets the requirements.
Example 3: The ratio of books and albums between Xiaoxue and Xiao Min is 7:5. If Xiaoxue sends 65 books to Xiao Min, the ratio of their books to photo albums is 3:4. How many books are there in Xiao Min?
175
Chinese public analysis: The ratio of the number of their books is 3:4, which means that the number of books in Xiao Min's original works can be divisible by 4 after adding 65, and only option A can satisfy the meaning of the question.
Example 4: In an English test, there were 265,438+00 applicants from the School of Mechanical Engineering and 65,438+030 applicants from the School of Architecture. It is known that the number of absenteeism in the two colleges is the same, and the actual reference number of the Mechanical College is 13/8 of the actual reference number of the Architectural College. How many people are absent from the exam in the School of Architecture?
A.2 B.4 C.9 D. 12
Chinese public analysis: From "the actual reference number of the School of Mechanical Engineering is 13/8 of the actual reference number of the School of Architecture", it can be known that the actual reference number of the School of Architecture can be divisible by 8, that is, one number in the 130 option can be divisible by 8, which may be the correct answer. If it is replaced, only option a is satisfied.
Of course, if you want to use the divisibility quick judgment option, on the one hand, you must learn to judge which problems can be solved by divisibility, on the other hand, it is also essential to master the divisibility judgment of common numbers. Chinese public education experts hope that all candidates can master these two points, and I believe that all candidates will be able to climb the mountain of mathematical operation and realize their dreams of public examination!