In addition, candidates who have never been exposed to this kind of questions at all, if they want to improve in a short time, it is best to master certain answering skills.
First, divisibility features can help candidates quickly start with the characteristics of the stem, extract the characteristics of which number the answer should be divisible by, and then combine the options to make the correct answer clear at a glance. But the premise of doing the problem quickly is to master the judgment method of divisibility: 2 divisibility, a number can be divisible by 2 if and only if the last digit can be divisible by 2. A number is divisible by 3,9 if and only if the sum of its digits is divisible by 3,9.
The company arranges employees to listen to the report in the meeting room. If every three people sit on a bench, the remaining 48 people will have no seats. How many employees listen to the report?
a、 128 B、 135 C、 146 D、 152
Answer B.
Analysis: According to every 3 people sitting on a bench, there are 48 people left. We can know that the number of people listening to the report can be divisible by 3, and the correct option is B.
Second, odd parity is so-called odd numbers like 1, 3,5 ... Strictly speaking, integers that are not divisible by 2 are odd numbers. Even numbers are usually called even numbers, such as 2, 4, 6, ... Strictly speaking, integers divisible by 2 are even numbers. The concept is simple, but more often it tests the properties reflected by the addition and subtraction of odd and even numbers:
Odd odd = even odd even = even even even = even even = even even.
Odd × odd = odd × even = even × even = even
Example 1: There are seven cups, all of which are facing up, and four cups are turned at the same time. After a few turns, the cup can sink.
A, three times b, four times c, five times d, not even a few times
Answer D.
Analysis: a cup, if you want to make your mouth face down, you must turn it odd times. If it wants seven cups, mouth down, it can be rejected. Because odd times and odd numbers are equal to odd numbers, the total number of times is also odd, and six times are turned at the same time, no matter how many times, the total number of times must be even. This is inconsistent with the odd number of times required for seven cups to face down, so it is impossible for seven cups to face down.
Example 2: Sum of1+2+3+...+1993 Odd or even?
Analysis: There are 1993 numbers in the stem, of which 997 are odd and 996 are even, so the final result is odd.
Third, the proportional method
Proportion, indicating the contrast between quantities. For example, there are both boys and girls in our class, and the ratio of boys to girls is 5:8, which means that boys can read 5 copies and girls can read 8 copies, which is also the core of the proportional method-the idea of number of copies. In this way, the number of 1 serving can be calculated, and the number of boys and girls can be calculated by using the number of 5 serving and the number of 8 serving.
For example, if the speed is increased 10%, we can arrive 30 minutes earlier than the original time. If you walk 2 10 km at the original speed, you can arrive 20 minutes earlier if you speed up by 20%. The distance between these two places is () kilometers.
a、300 B、330 C、350 D、420
Answer B.
Analysis: in the first case, the original speed: the current speed = 10: 1 1, the distance is from a to b, and the speed and time are inversely proportional. Original time: current time = 1 10, with a difference of 30 minutes. In the second case, the original speed: the current speed =5:6, the original time: the current time =6:5, with a difference of 20 minutes, and the original time is 120 minutes. In these two cases, 210km represents the driving distance of 210min, and the original speed between the two places takes 330min, which is the distance.
The above three problem-solving skills are all based on the numerical characteristics of questions, which saves time compared with traditional formulas and equations, but candidates need to master the application environment of these skills in order to reach the realm of skilled application. I wish the landlord a smooth landing.