When we finished buying what we needed, we were about to leave. I saw sausages on the shelf, so I asked my mother to buy some sausages, and my mother agreed. But just after a few steps, I saw a package with the same brand and weight on the shelf, which contained 10 pieces at 4.30 yuan each. Do you want to buy a pack or a slice? I hesitated. Suddenly, my mind turned and I understood. Just compare and see which one is cost-effective. So I started to calculate: if I buy 10 pieces in retail, each piece costs 40 cents, which is equal to 4 yuan, and the whole package costs 4.30 yuan, which is 3 cents more, so I decided to buy it in bulk. I told my mother the process of my calculation, and my mother praised me for my love of brains.
Mysterious leap year
Today, when reviewing the time unit, the teacher mentioned a leap year in a normal year, that is, a year that only happens once every four years. That year, there will be 29 days in February and 366 days in the whole year, which I can understand, because the time for the earth to make a revolution is 365 days, which is about 1/4 days. Four years later, there will be one more day, which will be added to February with the least number of days.
However, what I can't understand most is why a year with an integer of 100 is a leap year if it is a multiple of 400. For example, 1900 and 1800 can be evenly divided by 4, so it should also be a leap year. Why must it be a multiple of 400?
In order to find the answer, I rummaged through the books, but I couldn't find the answer. I only got one data. The revolution time of the earth is 365 days, 5: 48: 46. I think, hey, maybe it can be calculated like this.
Let's get started. I'll convert 5: 46 seconds into 20926 seconds, and there are 86400 seconds in a day. 20,926 ÷ 86,400 ≈ 0.2422 (days), which is the number of days that people miss every year, so this number multiplied by 4 equals 0.9688 days, and people regard it as a day for simplicity, thus adding 654,300 days. When 46 minutes is 4.8 seconds ×( 100÷4)= 19, 12 minutes, that is, the extra time calculated every hundred years, people regard these times as other 99 years (100- 1). Every 400 years, there are 4.8× (400 ÷100) =19.2 days, nearly one day, so there is another leap year in 400 years, that is, 100-3=97 (one), so there are only 97 leap years in 400 years.
Oh! It turned out that many things have finally figured it out. Although it was troublesome, it also untied one of my knots. It feels great. In fact, mathematics is very close to our life, almost everywhere, as long as we work hard, there will be a lot of gains!
Topic: Grade Three-math diary!
Date: 2005-12/06
Content:
1The weather will be fine on Friday, October 25th.
Today, the second class is math. Our class has learned: distance = time * speed. We are very happy!
165438+1Monday, October 28th is fine.
Today, I learned a question I came up with. Xiao Qiang walks 65,438+000 meters per minute, while Xiao Li walks 65,438+050 meters per minute. They walked across from Party A and Party B and met in four minutes. How many meters is there between A and B? The answer is: 4* 100=400 (meters); 4* 150=600 (m); 400+600= 1000 (meter). Did you do it right?
Li Qing
answer
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Author: Fish Xiang shallow bottom
Date: 2005-12/06
Content:
Friday, October 25th, 2005/KLOC-0 +065438.
This morning, we learned speed * time = distance. Based on this, I can also derive three formulas: time * speed = distance; Distance/time = speed; Distance/speed = time. I am very happy today! By the way, did you launch it?
Monday, June 28th, 2005 +065438+ sunny.
This morning, we learned speed and * meeting time = total distance. Then we can deduce: the sum of meeting time * speed = the total distance without learning; Sum of total distance/speed = meeting time; Total distance/meeting time = total speed. Did you also derive it by multiplication and division?
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Author: Fish Xiang shallow bottom
Date: 2005-12/06
Content:
1The weather will be fine on Friday, October 25th.
Today, in the second class, both the teacher and the headmaster came, and the class was very quiet. We know the distance. Oh, I almost forgot. The teacher also asked us to learn how to walk with robots. I also learned "speed * time = distance". I changed this formula to "distance/time = speed". This course is really interesting.
I'm going to write this math lesson down in my notebook.
Zhang Xiangyu
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Author: Fish Xiang shallow bottom
Date: 2005-12/06
Content:
165438+1Monday, October 28th is fine.
Today, we learned the circumference in class. We also learned: speed * time = distance. I also wrote three according to this formula: "time * speed = distance; Distance/time = speed; Distance/speed = time "formula. Perimeter means: the length of a graph in a week (the sum of all edges surrounding a graph) is called perimeter. What a great harvest today!
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Author: Fish Xiang shallow bottom
Date: 2005-12/07
Content:
Friday, October 25th, 2005/KLOC-0 +065438.
Today, in the second class, three vice principals and Mr. Fu from No.3 Middle School came to listen to our class. The first one is robot walking. Let's do a problem. I said a method that my classmates didn't know and got a small sun.
Liluyang
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Author: Fish Xiang shallow bottom
Date: February 7, 2005
Content:
165438+1Monday, October 28th is fine.
There are three questions on page 83 of People's Education Edition tonight. I am very happy. I even did all the questions on page 83. I checked myself, and I think I did everything right.
Chen Yuxin
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Author: Fish Xiang shallow bottom
Date: 2005-12/07
Content:
Monday, June 28th, 2005 +065438+ sunny.
Today, we have a preliminary understanding of the problem of distance. On Friday, we learned a formula: time * speed = distance. Today, we learned another formula: speed and * meeting time = total distance. After a while, the teacher asked us to do a distance problem by ourselves. The teacher gave us some information: the train runs 25 meters per minute; The car travels 23 meters per minute; The plane flies 300 meters per minute; Supersonic planes fly 800 meters per minute, and so on. I said: From Shunde Road to Xinxi Street, the car and the train walked in opposite directions and met in two seconds. What is the distance between Shunde Road and Xinxi Street?
Liu
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Author: Fish Xiang shallow bottom
Date: 2005-12/07
Content:
Friday, October 25th, 2005/KLOC-0 +065438.
In the second class today, the teacher talked about: understanding the simple distance problem. I know: speed * time = distance. I am still using this formula!
Qu Shuo
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Author: Fish Xiang shallow bottom
Date: 2005-12/07
Content:
Monday, June 28th, 2005 +065438+ sunny.
Today, someone in our class came to attend the lecture again. Our math teacher said: speed and * meeting time = total distance, I remember them all. Thank you, teacher, for telling our class new knowledge. Last Friday, we also learned time * speed = distance. I'm so happy! Thank you teacher!
Gio Xiao Ya
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Author: Fish Xiang shallow bottom
Date: 2005-12/07
Content:
1The weather will be fine on Friday, October 25th.
Many teachers came to the second class today. The teacher asked us to learn to walk with robots. We all worked out a formula through robot walking: speed * time = distance. This course is really interesting!
Gao runqing
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Author: Fish Xiang shallow bottom
Date: 2005-12/07
Content:
Monday, June 28th, 2005 +065438+ sunny.
Today, the teacher taught us to learn: at the same time, separation, opposition and meeting. I also know what they mean. At the same time, it means starting at the same time. Distance is distance. Relative means: two people are relative. Meeting is meeting. Today, I not only learned this knowledge, but also learned: speed * time = distance and speed and * meeting time = total distance.
Okay, Meng Meng.
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Author: Fish Xiang shallow bottom
Date: 2005-65438
Content:
Friday, October 25th, 2005/KLOC-0 +065438.
Today, I learned: speed * time = distance. I can change it to: time * speed = distance; Distance/time = speed; Distance/speed = time. The teacher also asked us to learn how to walk by robots. I am very happy today!
Monday, June 28th, 2005 +065438+ sunny.
Today I learned: speed and * meeting time = total distance. I can change it to: meeting time * speed and = total distance; Sum of total distance/speed = meeting time; Total distance/meeting time = speed and sum. Besides, the headmaster and the teacher are listening in the back. But we are not nervous at all.
Shang pengna
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Author: Fish Xiang shallow bottom
Date: February 8, 2005
Content:
1The weather will be fine on Friday, October 25th.
I went to Xiao Ming's house to play and saw a Little Square in his house. I asked Xiao Ming, what is the side length of this square? He said, I don't know, only that its circumference is 36 cm. I think: a small square has four sides, and each side is equal in length. Then I'll use 36/4=9 (cm). I am glad to tell Xiao Ming that the side length of this small square is 9 cm. Xiao Ming is measuring. He said, yes! Let's play together.
1Saturday, October 26th, sunny
I found a small wallet on the road and waited for the owner in the same place. At the same time, I measured its circumference as 30 cm and its length as 12 cm. Measured here, I calculated its width as: (30- 12*2)/2=3 (cm). It was measured again, and it was correct. After a while, the shopkeeper.
165438+1Monday, October 28th is fine.
Today, the teacher teaches students speed * time = distance and speed * meeting time = total distance. I remember. I can also apply and transform it. It's like this: time * speed = distance; Distance/time = speed; Distance/speed = sum of time and meeting time * speed = total distance; Sum of total distance/speed = meeting time; Total distance/meeting time = speed and. I feel great!