In a shopping mall, after 8: 00 p.m., the whole merchandise will be discounted by 9.5% on the basis of the original discount, which will be reduced by 100 yuan when it reaches 400 yuan. It is known that a shoe cabinet has a 15% discount. At 9 o'clock in the evening, someone went to the shoe cabinet and bought a pair of shoes, 384.5 yuan. What is the original price of this pair of shoes?
From 550 to 600 A.D.
Analysis: conventional solution: suppose the original price is a, the equation is 0.95× 0.85a = 384.5+100 = 484.5, and the solution is x=600. (Calculation process takes 1 min).
Spike actual combat method
Looking at the number 484.5, it is analyzed that 484.5, 4+8+4+5=2 1 can be divisible by 3, but neither 0.95 nor 0.85 can be divisible by 3, so A will be divisible by 3 and kill B.
Laying a water pipeline can be completed in 8 days by Team A alone, while Team B can lay 50 meters every day. If Team A and Team B are laid at the same time, 2/3 of the total length can be completed in 4 days. What is the total length of this pipeline? ( ).
A. 1，000m B. 1， 100m C. 1，200m D. 1，300m。
Routine exercise and training course exercise: Method 1: Assuming the total length is s, then 2/3×s=s/8×4+ 50×4, then s= 1200.
Method 2: 2/3 of the total length can be completed within 4 days, which means that it takes 6 days to complete * * *, 6 days for both parties,1/6-1/8 =1/24, which means that it takes 24 days for Party B to complete, and 24× 50 =1.
Spike actual combat method
Mathematical connection method completes 2/3 of the total length, that is to say, the total length is a multiple of 3. Choose C. 10 seconds to choose the answer.
Many math problems, even difficult problems, in the public examination can be solved quickly by spike method, and some can be applied to spike method with a simple transformation, which greatly simplifies the difficulty of the problems.
(09 Zhejiang Zhenti)
1 3 1 1 67 629 ( )
a . 2350 b . 3 130 c . 4783d . 778 1
Solutions to routines and training courses: Numbers rise faster, starting with square, multiplication and cube. Let's start with the most familiar numbers: 629=25×25+4=5 to the 4th power +4 67=4 to the 3rd power +3, and then we can deduce the 0th power of 1= 1 and the 1 power of 3=2. =6 to the fifth power +5=778 1 It takes at least 1 minute from thinking to solving the answer.
1 3 1 1 67 629 () According to the rising trend and trend of multiples, the question mark must be greater than 10 times. Only item D of ABCD option conforms to the multiple trend between two numbers: to be exact, it should be 13 times, which can be considered as follows: the multiples are about 3, 4 and 6 respectively. ), the difference shows that the question mark is about 13. There must be more than ten question marks.
Seconds kill the actual combat method, which can quickly give questions. This question is a trap set by the proposition group for candidates. If you do it blindly, it will be a difficult problem. You may not do it during the exam, or you will waste the exam time. The shadow of doing the problem will definitely affect the performance of the exam level in your mind. The second kill method will greatly save the time of doing math problems, thus leaving enough time for writing, logic, etc. to do problems and laying the foundation for getting high marks in the exam.