Last time we visited the percentage of old friends, this time we will continue to explore the percentage of old friends. Last time, I only discussed the first wisdom gate of percentage application (1), that is, the application of finding the phase difference first and then dividing it by the unit 1; After that, let's visit the second door of wisdom. Do you have the courage to accompany me to explore? Come if you have it!
As soon as I entered, I saw a problem that must be understood. For example, the price of an induction cooker in Sunshine Supermarket is 320 yuan, which is cheaper than the original price in 80 yuan. The price of induction cooker has dropped by several percent. Let's explore slowly. Teacher Zhang told us: Is this a kind of percentage application? Reverse narrative? When we encounter these problems, we should finish the key sentences first. For example, we add the price of 20 yuan in front of 80 yuan, which is cheaper than the original price, so that we can explore better. We can calculate the unit 1 first, and the original price: 320+80=400 yuan, and we know the difference (80). Then we divide the first 80 by 400, which equals 20%. We got the key to the second small door, and we continued to open the second small door. We only know the difference when we see one formula. Find the unit 1 first, then divide the difference by the unit 1. We explored the second wisdom door of percentage, and I learned a lot. Now let's compare.
The first is that we don't know the difference, and the second is that we know the difference; The first is that we know the unit 1, and the second is that we don't know the unit 1. The first one is easier for us to do, just find the previous difference and divide it by the unit 1. The second one is a little more difficult, but we just need to complete the sentence, then find the unit 1 and divide it by the unit 1.
2. Select 500 words of math diary in primary school.
After lunch at noon, I had nothing to do, so I picked up a book called "Top Student Question Bank". Open the chapter on negative numbers, read the previous explanation, and turn to the exercise section to do exercises. I watched the exercises first. Although there is a lot of content, it is easy. Thought: Hi! This is also called "top student question bank". It's so simple that I can do it with my eyes closed. So, I began to do the questions, fill in the blanks and judge the questions. I made two pages in a short time. Speaking of application problems, I thought it would be more difficult, so I read it carefully. This is not difficult at all. After two or three strokes, only one application problem was written. I have a cursory look at the problem. No, didn't I give the speed? What are these+15 and 15 for? I'll think about it. It's like mountains and rivers, and there's no way out. I read the question again, but I still can't. At this time, I thought of a formula I saw in a book, which seemed to be just right for this problem. I quickly turned out all the reference books on mathematics I bought, and read and reread them. Why not? I clearly saw this formula in the book, how could I not find it? Facts are facts, so I flipped through the answer in the back: 200? (35+ 15)+200? (35- 15)= 14 hours, why should we divide 200 by 35? At this time, in the question of travel, I picked up the book "General Review of Primary School Graduation" and turned to the page about travel. There is a formula that makes me suddenly realize that it is like this: distance divided by speed equals time, and these plus fifteen and minus fifteen are addition and subtraction, not symbols.
Math problems really need to be understood carefully!
It seems simple, but in fact it contains complexity. Whatever you do, be serious and don't underestimate it.
3. Select 500 words of math diary in primary school.
During the winter vacation, I took part in a math interest class. The teacher was a beautiful young female teacher, Miss Chen. Teacher Chen gave us a unique first lesson. First of all, the first question she asked us was: What is mathematics? Although this question is simple, it is full of mystery, and I can't answer it, but there are still many students who enthusiastically raise their hands to answer the question. Mathematics is common sense used in life and an expression of our thinking. Mr. Chen seems to be very satisfied with mathematics. He said: the students' answers are wonderful, but they are not completely correct. Mathematics is a subject that studies concepts such as quantity, structure, change and spatial model. By using abstract painting and logical reasoning, the shape and movement of objects are counted, calculated, measured and observed.
Teacher Chen told us about mathematics and the significance of its existence. She said that mathematics is not to do problems rashly, but to exercise our thinking and make our thinking stronger and stronger, so that we can judge a thing quickly. Mathematics is a subject. If you are interested in mathematics, then your thinking is already very strong.
Yes, through teacher Chen's teaching, we gradually understand the meaning of mathematics. Some math problems may be difficult, but every time we solve a problem, we can exercise our thinking. For example, Mr. Chen asked us to spend half an hour doing a problem, which is the third grade problem. Even if you can do it, you have to do it for half an hour:
A classmate found that the price of his walkman was the same in two supermarkets, A and B, and the unit price of his schoolbag was the same. The sum of the unit price of the walkman and the schoolbag is 452 yuan, and the unit price of the walkman is four times less than that of the schoolbag, 8 yuan.
What is the unit price of the walkman and schoolbag that students like? Although this question is difficult, you can write it according to your own understanding. Exercise your thinking and improve your math ability!