Last night, it was very hot. Dad stopped me when I took out a watermelon to cut. He gave me a question, the title is: cut this watermelon into nine parts and cut out ten skins. See how you cut it? At this point, I thought, well, it's simple. So, I went to get a fruit knife, put the watermelon on the table and cut it. I cut a "meter" shape. If you count, nine dollars is enough, but only nine dollars! Not convinced, I brought another watermelon. When I was about to cut it, my father stopped me. He pointed at me and said, "Oh, how many watermelons did you waste?" Let me cut it! "Dad picked up a fruit knife and told me to watch. I watched the audience carefully. At this moment, a question mark flashed through my mind. What should I do? After dad cut it, I counted it. There were only nine skins, but he cut it in the shape of a well. I looked at my father and said, "Dad, didn't you cut nine pieces?" Dad saw my puzzled look and told me the "hiding place" of the tenth piece of leather. It turned out that the tenth piece of skin was hidden under the mouth in the middle of the word "hmm" before I suddenly realized.

At this time, my father looked at me and guided me according to the situation: "There are many things in life. As long as you observe carefully, you will definitely gain something, just like cutting watermelon this time. " I nodded my head.

At noon today, I was doing my math summer homework. Writing, unfortunately, I have a problem. I thought about it for a long time, but I couldn't figure out a way. The question is this:

There is a cuboid, the product of the front and the upper two areas is 209 square centimeters, and the length, width and height are prime numbers. Find its volume.

I saw it and thought: this question is really difficult! Only knowing the product of two surface areas, the volume must also know the length, width and height, but there is no hint at all. How does this start?

Just as I was scratching my head, a colleague of my mother came. He taught me to use the idea of equation to solve it first, but I am not very familiar with this method of equation. So, he taught me another way: list the numbers first, and then exclude them one by one. First, we listed a lot of numbers according to the requirements of the topic, such as: 3, 5, 7, 1 1, and then we began to exclude them, and then we found that only1and 19 were left. At this time, I thought: one of these two numbers is the length of the common side of the front of the cuboid in the question; One is the front of the cuboid, and the other is the division of the previous one.

Sum of side lengths (all lengths are prime numbers). So, I began to tell which number these two numbers were.

Finally I got the result, which is 374 cubic centimeters. My formula is: 209 =119 = 2+171× 2×17 = 374 (cubic centimeter).

Later, I checked this problem with what I learned this semester: prime factor decomposition, and the results are exactly the same.

I am happier than anyone to solve this problem. I also understand the truth that mathematics is full of mysteries, waiting for us to explore.

Math diary in the fourth grade of primary school, math diary with the word 100.

It will be sunny on Sunday, September 26th.

I didn't do very well in the last unit test. The second minor problem in question 8 is the one with the most points deducted. The topic says that the clothes donated in the fourth grade are between 14 10 and 1470. Please list the possible works in descending order. I thought it was to write the numbers 14 10 to 1470 and the middle number. In fact, it is to write the numbers from 1420 to 1460. Be sure to keep this topic in mind this time, and you must do it next time you encounter this type of topic.

Math diary

165438+1October 14 Sunday rain

Last Saturday, I went to school to participate in interesting math activities in Grade Three. When we got to the delivery room, we sat in the position designated by the teacher. After a while, the class began and the teacher began to lecture. At first, I listened carefully. However, the more I listened, the less serious I became. In order to do our homework well, the teacher asked us to queue up for approval. When it was my turn, I really made a mistake. Then, I revised the topic and gave it to the teacher for approval. This time, the topic is finally right. Alas, I

What a pity: I shouldn't be absent-minded in class.

Math diary

It will be fine on Sunday, June 6th.

Last time, the teacher gave us the mid-term exam in the math workbook. I only got a score of 109, which was deducted from a very simple oral calculation problem. I crossed the math problem vertically on a blank sheet of paper several times and got it right. I copied it wrong when I copied it down. Well, why can't I get rid of my carelessness?

Math diary

It will be sunny on Sunday, September 12.

Today, my mother and I went to the supermarket and didn't buy anything. My mother gave me 10 yuan to buy what I wanted. I bought bubble gum from 2 yuan, two packages of soft candy from 2 yuan, two packages of xerox chips from 6 yuan, and a *** 10 yuan. Mother bought two bags of toilet paper 4 yuan, two bags of paper cups 7 yuan and a toothpaste 3 yuan. Mom spent 14 yuan. My mother and I spent 24 yuan.

Math diary

Three children, A, B and C, went for an autumn outing. A brought four loaves, B brought three identical loaves, and C brought no bread. At noon, three people will share it equally. After eating, C takes out 2 yuan 1 jiao as bread money. How much do Party A and Party B each want to recover?

Since the seven loaves are shared equally by three people, the price of each person's bread should be equal. C paid 2 yuan 1 angle for the bread, so the total price of the seven loaves is 2 1×3=63 angle, and the price of each loaf is 63÷7=9 angle. A brought four loaves of bread at a price of 9×4=36 cents. After deducting the price of bread he ate, 2 yuan 1 jiao, he should get back 36-2 1= 15 jiao, that is, 1 yuan 50 jiao; B brought three loaves of bread, and the price was 9×3=27 cents. After deducting the price of the bread he ate, he should get back 27-2 1=6 cents.

Math diary

101October 5th

Tuesday

very good

Today, my mother asked my brother and me to write a composition. My brother and I are writing carefully. After a while, we both finished writing. I wrote 1 150, and my brother wrote 1 149. Mother asked my brother and I to write more words than anyone else. Here's my calculation:

1 150 & gt； 1 149

Mother asked, "How did you work it out?" I said, "I'll compare the figures in 1000 places first, and the figures in 1000 places are the same, so I'll compare them with the figures in 100 places, and the figures in 100 places are the same, so I'll compare them with the figures in 10 places." I am older than him in the top ten, so I write more words. "

Math diary

165438+1October 14

Sunday

light rain

Today, my mother bought a box of 6 kilograms of milk and 500 grams of meat. I want to count how many grams my mother bought. It suddenly occurred to me that the teacher said the same topic in class, that is, convert different units into the same one, and then add the two numbers. So, I converted 6 kilograms into 6,000 grams, and then 6,000 grams +500 grams = 6,500 grams. This is really an easy math problem to do.

play darts

play darts

Today, my father and I went out to buy darts. When I got home, my father hung darts on the wall, played with me and taught me how to keep score.

This dart is circular and divided into four circles along the radius. The central red circle is 50 points, the second green circle is 25 points, the third red and green circle divides the line ditch 3 times, and the fourth red and green circle divides the line ditch 2 times. The outermost part consists of 20 black and white cells, and each cell corresponds to a score. Black, white, red, green and stainless steel gaskets form a beautiful pattern.

There are six darts. At first, we didn't follow the rules of the game, but each person threw darts three times to see who scored the most, so as to decide whether to win or lose. For example, a score of 20, a score of 7 for 3 times, and a third score of 18. How to calculate? That is 7×3+20+ 18 = 59 points.

Playing darts not only exercised my oral expression ability and hand-eye coordination ability, but also brought me a lot of happiness. I like playing darts.

Thinking after learning difficult problems

I learned a difficult problem today, and I feel very good. Because I used my brain. Dad said, "If you can't, use your head and think more." For example, I saw a topic: 388÷4. Do you know what this is? We haven't learned how to divide three digits by one, but I want to try. This is how I calculated it at first. 3 is not enough to divide by 4. I can add up 8 and divide 38 by 4 to get 9. I thought, what about 4×9=36? Hey! Yes, put 38-36=2, then add 8 to 2 and use 28÷4=7. I said happily, "This question is equal to 97!" "Dad praised me.

Please?Save?Water

In math class, the teacher asked us to do a small experiment to predict how many glasses of water a day would be wasted if a faucet was not tightened. The steps are to fill a paper cup with water; Punch a small hole in the bottom of the paper cup with a pin; Let the water leak into the box and start timing.

The students started the experiment according to the steps. During the experiment, some students enlarged the hole at the bottom of the cup and the water flowed quickly. It took 10 minutes to leak a glass of water. If the hole is smaller, the water will flow slowly, and it will take 15 minutes to leak a glass of water. Through this speed test, it reminds me that if the faucet is broken, it wastes 4 glasses of water an hour and 96 glasses of water a day. China has a population of 654.38+03 billion and more than 600 cities, half of which are short of water. If everyone saves a glass of water, it can save 654.38+0.3 billion glasses of water, so saving water is very important for our country.

Through today's study, the students all understand: save water, start with me.

rope skipping

Teacher physical education class taught us to practice skipping rope today. Xu Zhen and Guo Yuan and I were grouped together. I jumped first, and Xu Zhen and Guo Yuan helped count. Jumped 150 times in 2 minutes. Then Guoyuan jumped. Xu Zhen and I help Guoyuan count. She jumped 180 times in 4 minutes. Finally, Xu Zhen jumped. Guo Yuan and I helped Xu Zhen count the number of people. She jumped 250 times in four minutes. Who jumps fastest among us? I calculated in my mind that I jump 75 times a minute (150÷2), Guoyuan jumps 60 times a minute (180÷3) and Xu Zhen jumps 65 times a minute (250÷4). I jumped for joy. Haha, I am still the fastest dancer.

Math diary in the fourth grade of primary school? Urgent need! click

:wenku . Baidu/link？ URL = LCD 9 be 1 jh0 xsnwavjbzjzr-Soh _ spdb 8 e 0 codcwyezlriooiirkynwfwsncfnrynmkbow 95 r 7 co 8 vbbgm 7 gxk 8 LQ 8 1 H5 ek 1 pobouebzooq

Math diary, a fourth-grade primary school student, is close to life. I won the prize. I just finished my homework tonight. At this time, the doorbell rang, and I was very happy, because I knew that this was my mother's return, and my mother had not chatted with me for a long time.

After the doorbell rang for five seconds, I quickly ran out of my desk to open the door. As soon as my mother entered the room, she said to me, "Hey, I brought back 1 box of Japanese chocolate!" I immediately cheered: "Yes, it's very kind of mom. Come, give it to me! " "Mom said," mom is not good. I can't just give you chocolate. You must answer my question. "After hearing this, I thought to myself: I am not afraid if you want to test me again!

Mom has a problem: I think it's a matter of reasoning this time. Xiaoming said to Xiaodong yesterday: "Yesterday, there were 10 students in our family. My mother took out a bag of sweets, which contained 54 sweets, and distributed them to small guests, but the number of each person was different. The most frequent one is 10. " Hearing this, Xiaodong immediately said, "You are lying! You lie! " I asked you why Xiaodong said Xiaoming lied. At this moment, I had a brainwave and thought that I had learned "simple reasoning" before. This question is different. I began to calculate: the most one got 10, so there can't be duplicate numbers. Let's assume that the first one gets 65,438+0 candy, the second one gets 2 candy ... and the tenth one gets 10 candy. Xiao Ming is lying, because he said that the bag of candy has 54 pieces, but actually one person wants 55 pieces, so Xiao Ming is lying.

I told my mother what I thought just now. My mother said I was smart, so she gave me this favorite Japanese chocolate. I think mathematics is really everywhere. Even I have to use math to get these chocolates. I got it, which is the crystallization of my efforts, hee hee!

Second, the fourth grade learned the decimal point in the next semester. I also know that when measuring and calculating, it is often impossible to get accurate integer results, so it is often expressed by decimal points.

The other night, I had a dream about decimal point. In a vast forest, the horn sounded suddenly. It turns out that the animal sports meeting officially opened today! There are several sports in the sports meeting. Among them, the most striking events are running, swimming and high jump. After fierce competition, the final result has been "released". The result of the running competition is that the pony runs 406.38+0 meters in one minute; The lamb ran 376.28 meters in one minute; The snail ran 129.726 meters in one minute. As a result of the swimming competition, Xiaoyu swam197.63m in one minute; The tortoise swam 184.52 meters in one minute; Tadpoles swim for one minute 152+0 meters. The result of the high jump is that the kangaroo jumped 2.35 meters; The rabbit jumped 1.89 meters; The frog jumped 1.642 meters.

When preparing to announce the result of the game, the fox said to the cow referee; "Cow referee, you see, this decimal point is as big as sesame. Simply put, don't use decimal points. " As she spoke, she erased the decimal point. As a result, the scores of each project have changed. The worst became the best. For example, the pony's running performance has become 4063 1 meter; The running performance of the lamb became 37628 meters; The snail has become 129726 meters. When everyone heard the result, they couldn't help asking: How did snails become running champions? Isn't he usually slow?

When I got up the next morning, I understood that if the decimal point is wrong, it will cause great mistakes. Tonight, my father mysteriously said to me, "Silver, I can do magic.". Do you believe it? " I can't wait to ask; "What? Do you know how to operate it? What massage is it? " "The magic is this: when you open a book, I can use magic to tell which side is an even page and which side is an odd page." Dad said proudly. Well, I don't believe it. I asked my father to demonstrate the massage on the spot.

I picked up a book and flipped through it quickly. When my father called "stop", I stopped turning the pages. Dad said with a slight air; "There are even pages on the left and odd pages on the right. I calculated, hey, awesome! Dad guessed right. Not convinced, I tried again and the result was still the same. I asked my father inexplicably, "Dad, how did you guess right?" Do you really have magic? "Dad answered me with a smile;" No, I didn't do it. According to the rule that there are even pages on the left and odd pages on the right of the book, I guessed right.

Today, I feel very happy because I have learned another math rule. Math is really interesting!

My sister and I are having a good time, and my grandmother insists on calling me and asking me to settle her account.

Grandma bought 3 Jin 4 Liang eggs, 3 yuan and 50 cents per Jin. Grandma handed it in 12 yuan. How much should I get back? As soon as grandma's voice fell, grandpa said, "Change 1 minute!" "I don't believe that Grandpa can calculate so fast, so I use the mathematical knowledge I have learned to calculate: unit price multiplied by quantity = total price; Spent money = recovered money, exactly the same as grandpa's, and the change is 1 minute. I asked grandpa why he calculated so fast. It turned out that Grandpa divided 3 yuan's five horns into five parts.

3 yuan +5 angle, first calculate 3.4 times 3= 10.2 yuan, then calculate 3.4 times 0.5, which is 3.4.

Half of it is 17 yuan, so a * * spent 1 1.9 yuan and paid 12 yuan, of course, a dime.

Yes After grandpa finished, I realized that he used multiplication and division.

Through this incident, I understand that mathematics can be used anywhere around us. Let mathematics serve us!

September

Hot spot: math diary in the fourth grade of primary school: How big is 100 million? It may be big or small. The big one can cover the earth for two weeks, and the small one may disappear in the blink of an eye.

In the fourth grade of primary school, the pronunciation of numbers within 100 million in math diary is divided into four groups, and the pronunciation of each group of numbers is within 10,000, plus the name of this section. For example, the first paragraph of 1369|8463 is 10000 and the second paragraph is 10000, so it is read as 13698463. You should adopt it! I was exhausted from playing.

Fourth grade math diary! Not long, not short! Urgent need! Math diary —— A Preliminary Understanding of Scores

( 1)

Today, my family went to KFC in Longgang for a family meal.

When we get there, people are always crowded. We finally ordered good food and found a seat to sit down. Here comes the food. This is a sumptuous set meal. There are 12 drumsticks in it. I thought: how to divide it equally? Then I remembered the division of 12÷3=4. We each have four drumsticks. Later, I ate my mother's 1 chicken leg and my aunt's two chicken legs. My aunt said, "You can't eat this for free. I ask you, how much did you eat? " How many more servings do you have to eat before you can finish them all? "I thought about it and replied," I ate 7/ 12, and then I ate 5/ 12. I ate all of it. "Fortunately, I learned the knowledge of fractions and can answer the questions correctly.

(2)

Today, my mother gave me 10 yuan to go shopping in the supermarket. I bought a string of firecrackers 2/ 10, four lollipops/10, seven balloons 2/ 10, and finally a comb 4/ 10, a *. There is still one yuan left, and I have to pay it back to my mother.

When I got home, my mother ate 1/4 lollipops, my father ate 1/4 lollipops, I ate 1/4 lollipops, and I gave the other one to my brother Xiao Qiang next door. (Author: Xiao Enling)

(3)

Last week, we studied fractions. Fractions have numerator, denominator and fractional line, for example, 1/3, where 3 is denominator, 1 is numerator and the middle horizontal line is fractional line.

Scores are used in many places in life. For example, a book has thirty pages, and each page is 1/30 of a book. Fractions can also be used to add and subtract! For example, half plus half equals two, which is 1. Why is this happening? If you divide a cake into two parts, each part is 1/2 of the cake, and then put the two parts together, there are two parts 1/2, which is just a cake. When adding and subtracting fractions, if the denominator is the same, only the numerator is added, regardless of the denominator. And 2/2 of the numerator and denominator are the same, which is 1.

I also learned to compare the size of fractions. The teacher taught us the formula: numerator is the same as denominator, the fraction with large denominator is small, and the fraction with small denominator is large; Denominators are the same as numerators, with large numerator scores larger and small numerator scores smaller.

The teacher also reminded us that when writing scores, we usually write the fractional line first, indicating the average score, then the denominator and finally the numerator.

Math diary (1), a 200-word math in the fourth grade of primary school, impressed me deeply.

Math, Math I love you, just as mice love rice. Do you know why I like math? Because of the charm of mathematics, it attracted me deeply.

I learned a new knowledge today, that is, the simple algorithm of addition and subtraction. After learning the simple addition and subtraction algorithm, my calculation speed is much faster and it is easier to learn to calculate. Give an example! For example: 367+498=? I just have to think like this: add up 498 to make 500, and then use 367+500. I found that I added 2 more, so I subtracted 2 from the total to get 865. And 796+295? I think so: 796 can be added to 800, 295 can be added to 300, one plus 4 and one plus 5, then the formula becomes 800+300-4-5= 109 1. Look, how convenient it is!

After learning the simple algorithm of addition, it is much easier to learn the simple algorithm of subtraction. Such as: 483-299, hehe, you can find the way by gently moving your head. I'll take 299 and subtract it from 300, because it's 1, so just add 1 to the result, which is 483-300+ 1= 184, and the calculation is much simpler. However, I can warn you: it's best not to think about the minuend when doing subtraction, or you'll be in trouble!

Now, I like math more and more, because it makes me learn to calculate the results quickly, and math really makes me remember deeply!

Preview is a golden key.

After math class today, the teacher arranged for us to preview division estimation.

What is a preview? Why does the teacher want us to preview? I came home with a surprise. Check the information and ask your parents. It turns out that preview is to read the contents of the book by yourself before learning a new lesson. Mark what you don't understand, and then listen carefully in class. ) In this way, you can have a preliminary understanding of new knowledge.

I previewed the division estimation curiously. Through preview, I know that when estimating 538÷62, 538 can be regarded as 540 and 62 as 60, so 538÷62≈9. It turns out that preview can help me clear away the obstacles in math learning and have a preliminary understanding of estimation. Can quickly accept new knowledge in class. Even if there is doubt, it can be easily solved.

Therefore, it is very important to preview before class, so we must develop the good habit of preview, because successful preview can make the lecture quality higher and the learning efficiency higher, so it is the golden key to open the door to knowledge.

(3) A special math contest

The annual math contest began. The forest is very lively. This year's contestants are: cotton seed, turtle, tiger and lion.

The game has already started. Teacher Swan first gave each of these candidates a test paper, and then said to them, "Whoever can calculate correctly and quickly in a certain period of time will win the Wisdom Cup Award."

As soon as Mr. Swan finished. These candidates began to write. Rabbits run fast and do fast. I saw that she was very clever and soon finished more than half of it. Come on, let's have a look at its test paper. "dizzy!" Look: 80-70= 150, 20 ÷ 4 = 80 ... What a mess! I didn't even see the operator number clearly

Look at lions and tigers. Hey! Why don't you see lions and tigers? I only saw a lot of manuscripts. Before I left, I saw lions and tigers busy! It turns out that every time a lion does something, he has to take out the manuscript paper to calculate. The more manuscripts are piled up, the more lion heads are hidden. Really simple-minded, developed limbs. Tigers are more exaggerated. Every time I finish a question, I will take out my manuscript and check it. No wonder you are sweating.

Finally, let's look at the tortoise!

The tortoise is usually slow-tempered, but this time its thinking is not slow at all. See how wonderful this question is: 3456-999 = 3456-1000+1= 2457. The tortoise uses a simple algorithm to finish the test paper quickly, and it is right and fast!

Finally, the tortoise won the wisdom prize.

(4) The importance is 0.

0 is a mysterious number, as elusive as the mystery in the universe. 0 is also an important number. If you accidentally add an extra 0 or a less 0, the consequences are really unimaginable.

This math exam really made me realize the importance of 0. It was 99 points when the test paper was handed out! I made a mistake at once. The result made me dumbfounded. The result is 4500÷90. "How could I make a mistake with such a simple question?" I muttered to myself. I remember that when I dictated the 45,000-90 question, I easily wrote down 50, and I was still very confident. But in the end, I got 500, which was a 0. How wrong it is! What should not be wrong is also wrong. How important 0 must be!

If I become the financial general manager of the company in the future and someone else comes to withdraw money, I would have taken 10000 yuan, but I added 0- 100000 yuan more, and I still put 10000 yuan on the bill. Then who should I ask for this 90 thousand yuan? I will bear all the consequences!