Urgent! ! ! ! !

--Kaleidoscope---Mathematics Diary of Sixth Graders

Sunny Wednesday, February 10

Ma Weili, Class Six (7), Eight Road Experimental Primary School

Use division to compare fractions

The sun is shining brightly today. I was watching the "Primary School Mathematics Olympiad" at home and suddenly found this question: Compare the two fractions 1111/111 and 11111/1111. . Suddenly, I became interested, picked up a pen and started drawing on the paper. After a while, I found a solution. That is to convert these two improper fractions into mixed numbers, and then use the law of fractions. With the same numerator and fraction, the smaller the denominator, the greater the fraction. Solve 1111/111<11111/1111. After I finished solving the problem, I was very happy and boasted: "It seems that no problem can trouble me." My mother, who was knitting a sweater, listened to my words, looked at the question, and laughed loudly: "Oh, I still can't solve it." I thought it was so difficult, isn't it just a simple comparison of fractions?" After hearing what my mother said, I immediately became angry and said, "What, this question is difficult." After that, I sarcastically said to my mother, "You're so difficult." Hey, this question is not a piece of cake for you!" Mom smiled: "Okay, okay, I won't argue with you, but if you can solve this question in two ways, then you are considered to be at a high level. "After listening to my mother's words, I looked at the question again and couldn't help but be stunned. "There is another solution," I said in surprise. "Of course," my mother said, "How about it, you can't do it, it seems you are still at a low level." I was very angry because of what my mother said, so in order to prove that I was a high-level person, I did it again. Finally, after some hard work on my part, the second method came out, which is to use division to compare the sizes between them. You see, if a number is smaller than another number, then the quotient of this number divided by the other number must be a true fraction. Similarly, if a number is greater than another number, then the quotient of this number divided by the other number must be greater than 1. Using this rule, I used 1111/111÷11111/1111. Since these numbers are too large, they cannot be multiplied directly, so I changed the division formula again. Assume that there are 8 1's, allowing you to form two numbers, What is the largest product of two numbers? Needless to say, they must be the two closest, so 1111/111÷11111/1111=1111/111×1111/11111, 1111×1111>111×11111, then 1111/111>11111/1111.

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--Author: Soaring< /p>

--Publish time: 2004-3-20 13:36:26

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Sunny on Friday, February 12

Ma Weili, Class 6 (7) of Balu Experimental Primary School

Today, I saw such a question in the mathematics 1+2 training. In a cube cast with a base area of ??648 square centimeters, two opposite sides Remove the largest cylinder as its base. What is the area of ??the remaining three-dimensional figure?

When I saw this question, I was confused and thought: How can I find the base area if I only tell it? My mother, who was sitting on the chair, looked at it and laughed at me and said, "Humph, you're talking about a high level, and you can't even do this question."

I know that my mother is using the stimulating method, and the purpose is Inflame my competitive spirit and let me finish this question. In order to make my mother think that her provocation method was successful, I went ahead and did it, but I couldn't figure it out no matter how hard I tried. But I didn't lose heart and kept doing it. I did it.

According to the picture (you need to draw a picture), you can find that when a cylinder is cut off, a hole the same size as the original cylinder comes out. Although this hole has the same volume as the cylinder, their surface areas are not the same, and It is two less base areas than the original cylinder.

So the remaining figure area should be equal to the area of ??the 6 faces of the cube minus the two bases of the cylinder + the sides of the cylinder.

The calculation formula is 628×6-628×3.14÷4×2+628×3.14

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--Author: Aoxiang

--Published time: 2004-3-20 13:36:49

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Sunny Saturday, February 14th

Ma Weili, Class 6 (7), Eight Road Experimental Primary School

Today is another sunny day, I was wandering on the street and suddenly saw many people gathering not far away. I ran there for a year and it turned out to be a prize-catching game. "Humph, what's so fun about catching prizes?" I said in annoyance. When the people next to me heard this, they quickly said: "It's not fun to catch prizes, but there are huge prizes, which is very attractive." I asked eagerly: "What is it? !" "50 yuan.

"The man said with big eyes. As soon as I heard this, I got excited, "Such an attractive prize, no matter what, I have to try it. "After that, I asked the shopkeeper how to catch it. The shopkeeper said: "This is 24 mahjong pieces. There are 12 5s and 12 10s written under the mahjong. You can only catch 12 mahjongs each time. If the total number of 12 mahjongs is is 60, then you can win a grand prize of 50 yuan. "I didn't roll up my sleeves after hearing this, took out 5 yuan from my pocket and gave it to the shop owner.

Although I can catch this 10 times, I still didn't get the grand prize. < /p>

After I got home, I thought about it and felt something was wrong. I thought that to catch 60 points, all 12 mahjong pieces must be marked 5. The best situation is to catch 1 for the first time. 5, the second time to catch 2 5s, the 3rd time to catch 3 5s... the 12th time to catch 12 5s, it will cost at least 6 yuan. But if the number of the mahjong numbers caught is 10 or some. It's the same, so how many times does it cost?

Finally, after some consideration, I finally figured out the problem. I quickly went to the street to find the person to settle the account, but he had already disappeared without a trace. Lost.

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--Author ：Soar

--Release time: 2004-3-20 13:37:21

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Sunny on Monday, February 16

Ou Chuang, Class 6 (7) of the Eight-Road Experimental Primary School

Title: There are two candles with different thicknesses. The length of the thin candle is twice the length of the thick candle. It takes 1 to light the thin candle. Hours, it takes 2 hours to light the thick candle. There was a power outage. I lit two used candles like this at the same time. When I called, I found that the length of the two candles was the same. How long will the power outage last?

Problem-solving ideas: If the length of a tall and thick candle is 1, the burning speeds are: (1) 1÷2=1/2 (2) 2÷1=2 If the power outage time is X hours, then the formula is : 1-1/2X=2-2X Analysis It is known that the thin candle accounts for 1/2 of the thick candle, and the thick candle is twice as long as the thin candle. Find the number of hours of power outage, that is, how long the first candle burns.

Solution: Suppose the power outage time is X hours

1—1/2X=2—2X

X=2/3

Answer: Power outage. Time is 2/3 hours.

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--Author: Aoxiang

--Published time: 2004-3-20 13:37:57

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Sunny Wednesday, February 18

Xu Ruixiang, Class 6 (7), Balu Experimental Primary School

This afternoon, I saw such a question on the "Double Color Course for Primary School Students"

The radius of the base of a cone is 8 decimeters, and the ratio of the length of the height to the radius of the base is 3:2. What is the volume of this cone in cubic decimeters?

Analysis: This is a word problem that combines proportional word problems with questions on cones. To find the volume of a cone, you need to know the base area and height of the cone. The base radius is told in the question, and the base area can be found, but the height is not known. It can be found based on a condition, and the ratio can be converted into a number. Knowing what fraction of the number is known, we can know that the height accounts for 3/2 of the base radius. After calculating the height, then calculate the volume of the cone according to "V=SH÷3".

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--Author: Soaring< /p>

--Release time: 2004-3-20 13:38:34

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Overcast on Saturday, February 21st

Wang Guangpu, Class 6 (7), Eight-Road Experimental Primary School

Little discoveries in life

This morning, I made a small electric lamp, using two batteries, a steel wire and a Made of small light bulbs, I prepared two light bulbs first, for fear that they would flash when playing at night. At night, I went out for a walk. I took out a small electric lamp and looked around. I found that sometimes a surface was illuminated and sometimes a line was illuminated. This was an unexpected discovery that brought me I became interested in exploring why and got the answer. It not only brought me an interest in mathematics, but also improved my new perspective on life. I hope that everyone will be diligent in discovery in life and be a good student who is good at observation and thinking.

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--Author: Soaring< /p>

--Release time: 2004-3-20 13:39:19

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Overcast on Sunday, February 22

Ma Weili, Class 6 (7), Balu Experimental Primary School

In the past few days, I have been thinking about another way to find the volume of a cylinder. Based on my feeling, I listed this formula: diameter × diameter × Height×3.14÷4.

When I got home from school, I started to prove whether this formula was correct. I tried it. Using the solution in the textbook and my solution to calculate the volume of a cylinder were exactly the same. I tried again. Tried many times with the same result.

I was very puzzled as to what my solution meant. After some thinking and proof, I found that the cylinder was regarded as a cube with equal diameter and height. Then find the volume of the cube, and then according to the ratio of the cylinder to the cube: 3.14:4, it becomes the volume of a cylinder.

This is just my personal idea. Fans are welcome to participate in the research and provide corrections.

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--Author: Soaring< /p>

--Publish time: 2004-3-20 13:40:00

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Sunny on Saturday, February 28

Hou Jing, Class 6 (7) of the Eighth Route Experimental Primary School

Today when I was reading the newspaper, I saw such a topic: Find the surface area of ??a cone.

[Title] A cone has a base diameter of 6 meters and a length of 5 meters from the apex of the cone to the base of any point on the circumference. Find the surface area of ??the cone.

Although I have not learned to find the surface area of ??a cone, I have learned the surface area of ??a cylinder. Through the problem-solving method of the surface area of ??a cylinder, I know that the surface area of ??a cylinder is equal to the area of ??one side plus two bases, and the surface area of ??a cone The surface area is a side area plus a base area, and the side is a fan shape. Although I have never learned it, I checked the information and found that the area of ??the fan shape is: the area of ??the fan shape = arc length × circle radius × 1/2, in the question We have been told that the length of any point on the circumference of the cone from the vertex to the bottom is 5 meters, the arc length is 3.14×6=18.84 (meters), the sector area is 18.84×5×1/2=47.1 (square meters), and finally the sector area is Adding the base area, we get the surface area of ??the cone: 47.1+3.14×(6/2)×(6/2)=75.36 (square meters).

Mathematics is the gymnastics of thinking. As long as we study hard and think well, we will definitely overcome difficulties and embark on the road to success!

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--Author: Aoxiang

--Published time: 2004-3-20 13:40 :31

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Overcast Saturday, February 27th

Ma Weili, Class 6 (7), Eight Road Experimental Primary School

Today, I After learning the basic properties of proportion, I feel extremely puzzled as to why the product of the external terms of a proportion is equal to the product of the internal terms. After much thought and hard thinking, I finally understood.

If b/a=c/d, expand a by d times. If you want to keep the ratio unchanged, you must also expand b by a times, which becomes bd/ad; then put the equal sign The d in the ratio on the right is expanded by a times. To keep the ratio unchanged, c should also be expanded by a times, which becomes ca/da. Then the ratio becomes bd/ad=ca/da. Eliminate the ad around the equal sign, so it becomes ad=ca.

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--Author: Soaring< /p>

--Publish time: 2004-3-20 13:41:01

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Sunny on Tuesday, March 2

Ma Weili, Class 6 (7) of the Eighth Route Experimental Primary School

Every Qingming Festival, there will be a sea of ??people on Jushan, so some scammers come up with some deceptive tricks to deceive people, such as: gambling with discs .

The props are very simple. Draw a large circle on a piece of wood, and fix a rotating pointer with a nail in the center of the large circle. The large circle is divided into 24 equal grids, and the needles in the grids can be rotated. The grids are written with 1-24 equal numbers respectively. There is nothing valuable in the odd-numbered grids, but almost all of the even-numbered grids are valuable.

The gameplay is also very simple. First dial the pointer to 1, then you move the pointer, and the pointer starts to rotate, and finally stops in a certain grid, and then press the number marked on the grid where the pointer is located. Then move the pointer to N-1 grid, where N is the number marked on the grid.

This is just a small math game. In fact, no matter which box you dial, you can only suffer losses, not gains. Because when the pointer moves to the odd numbered grid, the number of the dialed grid is odd number - 1 = even number, odd number + even number only equals odd number, so it is impossible to turn to the even numbered grid, and you will not get valuable things. If the pointer turns to On the even grid, the number of grids toggled is even number - 1 = odd number, odd number + even number = odd number, and you cannot get anything valuable.

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--Author: Soaring< /p>

--Publish time: 2004-3-20 13:41:37

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Sunny on Monday, March 8

Today I listened to an open class on using multimedia to teach "Prime Numbers and Composite Numbers". After listening to it, I had some emotion. Originally, the use of multimedia in teaching was an organizational method to help teachers, and it can better facilitate teaching. services, increase the novelty, uniqueness, deepening of teaching, and make it more attractive. It has been proposed to provide quality teaching to students for such a long time, but after listening to several classes that use multimedia for teaching, they all showed the injection of Shadow, yes, injection into teaching has taken root before, but we must slowly change it in daily teaching; on the other hand, using multimedia teaching can better mobilize students' enthusiasm. Teaching is about serving students, not about computer services. Can it elicit cries from the majority of front-line teachers?

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--Author: Soaring< /p>

--Publish time: 2004-3-20 13:42:16

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Sunny on Saturday, March 6

Hou Jingjing, Class 6 (7), Eight-Road Experimental Primary School

Today is a sunny noon. I was reading a math journal at home and accidentally saw the question of finding ratios and simplifying ratios. I thought this was not from last semester. Have you learned it? But then I thought again, I might as well take a look!

There are differences and connections between "finding ratios" and "simplifying ratios". Students should pay attention to the following points when studying:

1. The purpose of finding a ratio is to find the result of dividing the first term of a ratio by the latter term; the purpose of simplifying a ratio is to make a ratio equal to it And the ratio of integers where the first and last terms are relatively prime.

2. The method of calculating the ratio is similar to that of simplifying the ratio. There are the following types:

(1) Use the basic properties of ratio. For example:

5/6:1/2= (5/6×6): (1/2×6) ① The ratio is 5/3; ② The simplification ratio is 5:3.

(2) Use the relationship between ratio and division. For example:

6.3∶0.9=6.3÷0.9①The ratio is 7;②The simplified ratio is 7∶1.

(3) Use the relationship between ratio and fraction. For example:

16∶20=16/20=4/5 ① The ratio is 4/5 or 0.8; ② The simplification ratio is 4:5.

3. The result of calculating the ratio is a number, which can be an integer, or a decimal or a fraction; the result of simplifying the ratio is a ratio, which can be written in the form of a true fraction or an improper fraction (see above For example), if it cannot be written as an integer, decimal or mixed number, the result of the simplification ratio should be read as a few to a few. For example: the simplification ratio of 16:20 is 4/5, which should be read as: 4:5.

It can be seen from this that as long as we read more information about mathematics, your grades will improve.

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--Author: Soaring< /p>

--Publish time: 2004-3-20 13:43:26

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Friday, March 12

Eight Road Li Tianli from Class 6 (7) of the Experimental Primary School

Calculating wages

At noon, my father came back from work, humming a tune and happily walked into the house. I went up to greet him and asked: "Dad, what are you doing today?" Are you so happy?" Dad said, "I got a salary increase this month.

I asked: "Then how much salary do you get per month now?" Dad thought for a while, smiled slightly and said, "My salary is higher than your mother's. Our combined monthly salary is 2,800 yuan. The monthly salary difference is 100 yuan. How much salary do you think I get per month?" ”

After listening to my father’s words, I started to draw a line diagram on the paper to help me understand:

Through observation and thinking, I quickly calculated the answer and told my father. First, consider the mother's salary as the same as the father. Then the monthly salary of the father and mother is (280100) = 2900 yuan. Then divide the monthly salary into two equal parts. The calculated one is the father. The monthly salary is: (280100)÷2=1450 yuan.

After hearing this, my mother nodded with satisfaction. Is there any other way? "Is there any other way?" "I said in surprise. I calmed down to observe and think again out of curiosity. I found that the key to this question is to find out who should be used as the standard. Different standards lead to different methods. So, I came up with a second The first method is to use mother's salary as the standard. Assume that father and mother have the same salary, then the sum of their monthly wages is (2800-100) = 2700 yuan, and then divide the monthly salary sum into two equal parts to find One share is the mother's monthly salary plus the 100 yuan more than the mother, and the formula is (2800-100) ÷ 2 + 100 = 1450 yuan.

After listening to me. The introduction of the second method made dad and mom laugh...

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--Author: Aoxiang

--Published time: 2004-3-20 13:44:00

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Sunny on Tuesday, March 16th

Hou Jing, Class 6 (7), Eight Road Experimental Primary School

The difference between volume and volume

Due to the calculation method of volume and volume The same, so many students think that volume is volume. In fact, volume and volume are two different concepts, and they are different:

1. Volume refers to the size of the space occupied by an object. , and volume refers to the volume of objects such as wooden boxes and oil drums. An object has a volume, but it does not necessarily have a volume.

2. The measurement method is different from the object. To calculate the length, width, and height from the outside, to find the volume of an object, you must measure its length, width, and height from the inside, and then calculate it. Therefore, for the same object, generally speaking, its volume must be calculated. Smaller than volume.

3. The unit names are generally used: cubic meter, cubic decimeter, and cubic centimeter. The volume unit of solids and gases is the same as the volume unit of liquid. The units are generally liters and milliliters.

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--Author: Aoxiang

--Published on: 2004-3-23 18:01:14

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Consider the overall situation

[Question] A numerical array with 8 rows and 8 columns as shown in Figure (1), where A, B, C, D, E, F, G, H, I, J, K, L, M, N , O represents 15 consecutive natural numbers from small to large. Divide this number array into four number array diagrams (2) with 4 rows and 4 columns. It is known that the sum of all the numbers in the fourth part of diagram (2) is 576. Let me ask, what is the sum of all the numbers in this number array with 8 rows and 8 columns?

Figure (1) Figure (2)

(Analysis and solution) When you see this question, you may take the work as the entry point, set it as The conditions provided form the fourth part of Figure (2) into an equation X+2(X+1)+3(X+2)+4(X+3)+3(X+4)+2( X+5)+X+6=576, find X=33, that is, I=33. Such 15 natural numbers are 25, 26, 27...39. After finding the size of each number, you can calculate the sum of all the numbers in Figure (2), which is equal to 2048.

Or after calculating the work, only H=32 is calculated. Then pair these 15 consecutive natural numbers in pairs to form the intermediate number H, A and O equal 2H, 2 B and 2 N form 4H, 3 C and 3 M form 6 H... Such a *** 56 H can be formed, plus the original 8 H, the total is 64 H. The sum of all numbers is 64×32=2048.

In fact, there is another simplest way to solve this problem. Consider it as a whole, that is, you do not need to find the specific size of any number on the array. You only need to compare the relationship between the four parts. .

The first number E in the second part is 4 less than the first number I in the fourth part, and the second number F in the second part is 4 less than the second number J in the fourth part..., Part Two Each number in is 4 less than the corresponding number in the fourth part, and the second part is 16×4=64 less than the fourth part. In the same way, the first part is 64 less than the second part. And the second part is equal to the third part. So the sum of all the numbers in this array is 576-64×2+(576-64)×2+576=2048.

Ma Weili, Class Six (7), Eighth Road Experimental Primary School, Pizhou City

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--Author: Aoxiang

--Published time: 2004-3-23 18:01:47

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Assume that the frog can continue to jump

[Problem] On the regular hexagon ABCDEF, a frog starts jumping at vertex A. It can jump to two adjacent vertices at will every time Above, if it jumps to point D within 5 times, it will stop jumping; if it cannot reach point D within 5 times, it will stop jumping after the 5th jump. Question: How many different ways does this frog jump from start to stop?

[Analysis and Solution]

This question can be divided into two situations:

1. Jump to point D within 5 times. There are 2 jumping methods: AFED and ABCD.

2. The frog jumped 5 times. Let's assume that the frog can continue jumping after jumping to point D within 5 times. Starting from point A, the frog has two ways to jump (to F or B). In fact, the frog has two ways to jump every time. According to the multiplication principle, if the frog jumps 5 times, there are 2*2*2*2*2=32 ways to jump. In fact, the frog jumps 3 steps and stops jumping at D, so the step of jumping to D and then jumping again needs to be subtracted. In the first case, it is clear that there are two ways for the frog to jump from A to D three times, and to jump two steps from D, there are four ways to jump: DED, DEF, DCD, and DCB. Again based on the multiplication principle, there are 2*4=8 ways to jump. So in this case, the frog has 32-8=24 ways to jump.

Based on the above two situations, the frog has 2+24=26 ways to jump.

Chao Xuerao, Class 6 (3), Eighth Road Experimental Primary School, Pizhou City, Jiangsu Province

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--Author: Aoxiang

--Published time: 2004-3-23 18:03:14

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Sunday, March 21, light rain

Hou Jing, Class 6 (7), Eight Road Experimental Primary School

Because of the rain today, I can't go out to play and have to stay at home When I was bored, I took out a mathematics newspaper from my schoolbag to read, and suddenly I saw: How to prevent writing 0 by mistake. Just as we are about to enter a comprehensive review, we have to review the reading and writing of integers at the beginning. Because in multi-digit reading, there are many situations when dealing with "zero". For example, when reading a "zero", some indicate one 0, while others indicate several 0s. Sometimes no 0 is read, but one or several 0s are written when writing a number. In this way, when writing multiple digits, it is easy to make errors of writing less or more 0s. How to prevent writing the wrong 0 in multiple digits? The following measures can be taken:

1. Write numbers by level.

When writing multiple digits, first find the words "100 million" and "10,000" in the grade names, and draw a vertical dotted line under each grade name to represent the grading line, and then in Wan Rong, Draw four short horizontal lines for each level, indicating that these two levels should be filled with four numbers. When writing numbers, first write 100 million, then 10,000, and finally 1. When writing ten thousand levels or one series, if there are less than four digits in each level, use 0 to make up the digits that do not have a unit.

2. Determine the highest bit and number of digits.

When there are two consecutive zeros in the multi-digit "level middle" and two or three consecutive zeros in the "level head", it is easiest to write less 0s. For example, the second number above was wrongly written as 32040009. If you can determine when writing a number that its highest digit is billions and has ten digits, you will immediately find that 32040009 must be written incorrectly because it is an eight-digit number.

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--Author: Soaring< /p>

--Publish time: 2004-3-30 15:37:43

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Sunny on Wednesday, March 24

Xu Ruixiang, Class 6 (7), Eight Road Experimental Primary School

The electric fan factory plans to produce 1,600 fans in 20 days. After 5 days of production, due to improved technology, work efficiency increased by 25%. How many days will it take to complete the task?

Analysis: This question can be solved by transformation and proportional method. Assume that the original efficiency is "1", then the actual efficiency is the original (1+25%) = 5/4, then the actual efficiency is the same as the original efficiency. The ratio of efficiency is 5/4:1=5:4. Because efficiency is inversely proportional to time, the ratio of actual to planned time is 4:5. If X days are actually needed, the original number of days is 20-5 =15 (days), therefore, the proportional method can be used to solve:

Solution, assuming that it takes X days to complete the plan.

4:5=X: (20-5)

5X=4×15

X=12

Answer: Complete The plan is to take another 12 days.

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--Author: Soaring< /p>

--Publish time: 2004-3-30 15:38:12

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Sunny on Wednesday, March 24

Hou Jing, Class 6 (7) of the Eighth Route Experimental Primary School

Number Legend

Someone said: "1, 2, 3, 4, 5, 6, 7, 8, 9, 0, Nothing in the world is possible without it."

Some people say: "Mathematics is so boring, ten numbers are turned upside down."

Two completely opposite views. Who is right? Who is wrong? Let the facts speak for themselves! In the 18th century, a British mathematician named Sanks spent nearly twenty years calculating the value of π to the 707th decimal place using only hand calculations. If numbers are really boring, can he endure loneliness for such a long time?

Chen Jingrun, a contemporary Chinese mathematician, used several sacks of papyrus in order to overcome the "Goldbach Conjecture". If numbers are really boring, where does his lasting interest come from? "Everything is number." The topsy-turvy 1, 2, 3, 4... contains infinite mysteries.

Both big and small "1"

1 is neither a prime number nor a composite number, it is the unit of natural numbers. Starting from it, 1, 2, 3, 4, 5... are arranged infinitely, forming a "digital army" with a beginning and a tail. The team is so big that it can circle the map countless times. Among them, 1 is the smallest, it stands at the front of the sequence. However, 1 is the largest. The entire earth, the entire universe, the entire... Just use 1 to summarize them all.

Human language is inseparable from 1 at all times: unchangeable, clear at a glance, feeling like old friends at first sight, three autumns in one day, ten cold weathers, one thought difference, one insight, one pillow... Look, this is disturbing The eye-catching 1, isn’t it interesting?

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--Author: Soaring< /p>

--Publish time: 2004-3-30 15:38:39

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Sunny on Saturday, March 27

Hou Jing, Class 6 (7) of the Eighth Route Experimental Primary School

Today, I seemed very bored, so I took out a "Mathematics Journal" and suddenly a very special topic attracted me.

[Title] There is a rectangular iron sheet. Cut out the shaded part in the picture to make a cylinder. The base radius of the cylinder is 2 decimeters. Then what is the square footage of the original rectangular iron sheet? Decimeter?

[Analysis and Problem Solving] If you look carefully at the picture on the right, you can find that the width of the shaded rectangle cannot be the perimeter of the base of the cylinder. Then, the perimeter of the base of the cylinder is the length of the shaded rectangle. In addition, , we can also find the width of the rectangular iron sheet, that is, the height of the cylinder is twice the diameter of the base of the cylinder, and the bottom diameter of the cylinder + the circumference of the base = the length of the rectangular iron sheet. Therefore, the length of the rectangular iron sheet is 2×2+2×3.14×2=16.56 (decimeter) and the width is 2×2×2=8 (decimeter). The original area of ??the rectangular iron sheet is 16.56×8=132.48 (square decimeter). .

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--Author: Soaring< /p>

--Publish time: 2004-3-30 15:39:19

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Sunny on Saturday, March 27

Cao Shaoqing, Class 6 (7), Eighth Route Experimental Primary School

Think about the problem based on reality

Think about it, where is his mistake?

[Title] There are two cylindrical wooden pillars in a certain hall. The diameter of the base of the wooden pillar is 0.6 meters and the height of the pillar is 6 meters. If you want to re-paint a layer of paint on their surface area, the paint How many square meters is the partial area?

After reading this question, Xiaoqiang felt that it was very simple. He quickly listed the formula and found out how many square meters the paint area was.

3.14×(0.6÷2)×(0.6÷2)+3.14×0.6×6×2=23.7384 (square meters). After carefully analyzing the meaning of the question, we can find that Xiaoqiang's idea is completely wrong. The reason for the mistake is that he does not think about the problem in light of reality. Although the wooden pillar is cylindrical, as far as practical issues are concerned, the painted part does not include the upper and lower bottom surfaces. Therefore, the required area of ??the painted part is to find the side area of ??the two cylindrical wooden columns. The formula should be: 3.14×0.6×6×2=22.608 (square meters). Answer: The area of ??the painted part is 22.608 square meters. .

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--Author: Soaring< /p>

--Publish time: 2004-4-2 14:05:25

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Sunny on Wednesday, March 31st

Hou Jing, Class 6 (7), Balu Experimental Primary School

Pairs of "2"

2. An even number is the smallest prime number and the only even number that exists among prime numbers. , "split into two". If any number is removed by 2, it will be divided fairly and no residual number will be left.

2. Reflects the two aspects of things: Yin and Yang, odd and even, heaven and earth, life and death, square and round, big and small, high and low, long and short, front and back. After and after, movement and stillness, virtuality and reality, black and white, noble and humble, poor and rich...etc., they are in pairs and interdependent, and they are indeed "unique and coincident"!

On a plane, a straight line can only be drawn with two points; an angle can be formed only when two straight lines intersect; two straight lines never intersect, which is called "parallel".

Look, 2’s magical power is powerful enough!

The perfect "3"

The ancient Greeks called 3 the "perfect number", saying that it embodies the "beginning, middle and end" and therefore has divinity.

In China, Laozi said: "Tao generates one, one generates two, two generates three, and three generates all things."

3. It is a very important link in the digital chain.

Three people are a crowd, three people are a tiger. When three people are walking together, there must be my teacher. A prism can analyze the spectrum. Einstein summed up the experience of success in three ways: hard work + correct methods + less empty words.

Look, it’s all “3” here!