A few days ago, math diary 1 in grade four, I read a piece of data in the newspaper: US$ 3.85 a gallon of gasoline, while China is RMB 1 liter of gasoline 6.6 yuan. I'm a little worried. I know this unit of volume, but how much is a gallon? What's its ratio to liters? With questions, I look up information online.
I regretted it as soon as I opened the webpage. The teacher told us that we should explore ourselves when we encounter difficulties, and it is best not to ask others for help if we can. I checked the information of gallon first and learned that it is also a unit of volume. I also found out the current exchange rate between US dollar and RMB, which is 6.5 yuan RMB exchange rate 1 US dollar. I decided to do the math myself.
3.85×6.5=25.025, and the data of 25.025 yuan per gallon is obtained. Know how much RMB is a gallon and how much RMB is a liter, and then use 25.025÷6.6≈3.79. It is concluded that 3.79 1 liter is approximately equal to 1 gallon. I checked online again, and the online admission rate was 3.785. Why is it different? I thought about it: it turns out that the entry rate of US dollars and RMB has been changing, so it will be somewhat different. However, rounding 3.785 is almost equal to 3.79 1.
The newspaper also said that the average annual income of Americans is about $36,000, or $3,000 a month. The average monthly income of China people is nearly 3,000 yuan. So Americans can buy 3,000 liters of gasoline a month, while China people buy only 6.5 times as much gasoline, about 462 liters.
They are all in RMB: Americans can earn almost 20,000 RMB a month, while China people are much less, only 3,000 RMB. Why is the gap so big? Because our country has not fully entered the fully mechanized production, there is still a lot of human labor. They pay as much sweat as rain, but get less reward. However, I believe that in the near future, China will develop better and stronger!
In fact, mathematics in life is everywhere. It may be just a sentence in the newspaper, just a sudden idea, or it may be a vision for the future.
Students of Grade 2 and Grade 4 in math diary once heard an Olympiad math teacher say: Learning math is like a fish like a net; Knowing how to solve a problem is like catching a fish and mastering the method to solve the problem, just like having a net; So the difference between "learning math well" and "learning math well" lies in whether you have a fish or a net.
Mathematics, a thoughtful course, is very logical, so it always gives people the illusion.
Geometry in mathematics is very interesting. Each number is interdependent, but it also has its own advantages. Such as a circle. The formula for calculating the area of a circle is because the radius is different, so we often make some mistakes. For example, "A pizza with a radius of 9 cm and a pizza with a radius of 6 cm are equal to a pizza with a radius of 15 cm". Proposition, this topic first confuses everyone and gives people an illusion. Using the formula of circular area skillfully makes people have a wrong balance.
In fact, a pizza with a radius of 9 cm and a pizza with a radius of 6 cm are not equal to a pizza with a radius of 15 cm, because a pizza with a radius of 9 cm and a pizza with a radius of 6 cm have the same area, so a pizza with a radius of 9 cm and a pizza with a radius of 6 cm are not equal to a pizza with a radius of 15 cm.
Mathematics is like a mountain peak, soaring into the sky. I felt relaxed at first, but the higher I climbed, the steeper the peak became, which made people feel scared. At this time, only those who really like mathematics will have the courage to continue climbing. Therefore, people who stand at the peak of mathematics all like mathematics from the heart.
Remember, people standing at the foot of the peak can't see the summit.
Math diary, a senior, was handed out on Wednesday morning. At first glance, it is "careless, careless, careless, careless!" I secretly scold myself in my mind. I only got 95 points in math and 94 points in Chinese this time. I suddenly turned pale. Chinese is passable, but math. ...
I came home depressed. After dinner, I took the paper and thought: Our "tigress" may treat me as a basketball racket, and my father will definitely nag like a monk chanting. Sign, sign, sign. I hate signing. The teacher has to ask parents to sign after doing so badly in the exam. At this time, my father came over, so I had to obediently give my father the test paper to sign. When my father saw that I did so badly in the exam, he frowned and shouted angrily, "What's the matter with you? You did so badly in the exam! " My tears suddenly ran down with disappointment. I said to myself, "Dad, I know I was wrong. I don't want to do so badly in the exam ..."
This roar attracted my mother who was washing dishes in the kitchen. She took my test paper and changed her face. "broken"! My heart is pounding, as if it stopped beating at once. I lowered my head to my chest and prepared to accept her "thunder and lightning". After waiting for a long time, my mother didn't make any noise. Somehow, the "tigress" turned into a docile "sheep" and said, "It doesn't matter if you fail the exam. The important thing is that you know where you are wrong and do better in the next exam. Just don't be so careless. " At this time, dad also became very kind.
I took a long breath and thanked my parents for their understanding. I am determined to study harder in the future.
Math diary, Grade Four, I just finished my homework this evening. At this time, the doorbell rang, and I was very happy, because I knew that this was my mother's return. My mother had not spoken to 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!
Math diary, Grade Four 5 Today, my father and I came to Huatang Commercial Building. First, let's buy clothes for dad. Dad picked out a dress that he particularly liked. It's just a 20% discount on the National Day special. Dad asked me that the price of a dress is 150 yuan, and a 20% discount is equivalent to multiplying the price of the dress by 0. 8. Do you know how much a dress costs? I want to put 0 first. 8 as 8, and then use the method of integer multiplication to calculate the result, and finally look at a factor * * *, how many decimal places there are, just count a few from the right side of the product number and point to the decimal point. The result is 120 yuan. I replied excitedly that the price of this dress after 20% discount was 120 yuan. Dad asked me again, "Usually when one number is multiplied by another, the product must be greater than the factor, but why is the product of this question greater than one of the factors?"
I think, in class, the teacher said. I said confidently, "The product of a number multiplied by more than 1 is less than the original number. Dad said, that's a coincidence. So is there such a rule for division? " "Of course, when the dividend is greater than 0 and the divisor is greater than 1, the quotient is less than the dividend. When the dividend is greater than 0 and the divisor is less than 1, the quotient is greater than the dividend. " Dad said, "Then I'll test you again. This dress is 50% off the original price in 200 yuan. What is the current price? " I quickly answered Yuan. Dad said happily, "My daughter has learned to extrapolate!" "
After buying clothes, we went to the underground supermarket. My dad told me: "The dairy products in the store are all on sale. If you buy two boxes, how much discount? " I said, "I don't know." Dad said, "buy two and get one free, that is, spend two boxes of money to buy three boxes of milk." A box of 50 yuan is equivalent to spending 1 yuan on 150 yuan's milk. Then dividing 100 by 150 is equivalent to his discount. The result was about 30% off. You got it? "I said," I see. "
It is increasingly found that mathematics is used to solve problems in life!
I have a very good friend in the fourth grade, math diary 6. He studies well, especially math. He is the first in his class every time, so the teachers like him very much. But what impressed me most was his attitude of studying hard and his spirit of helping his classmates enthusiastically.
He is not tall, thin, and his black hair shines especially in the light. He always has a bright smile on his face. He is good at sports and is a "sportsman" in our class. He loves the group and cares about his classmates. If his classmates have questions that they don't understand, he will always help others enthusiastically and explain patiently. He is the monitor of our class, and we all call him "Chicken Ding".
One Friday, the math teacher sent us a paper as our math homework. The questions on the test paper are so difficult that I don't understand any of them. On Saturday morning, as usual, I got up again and began to do my homework. As I was writing this question, I couldn't figure it out. It is really "there is no way to solve doubts." Suddenly, it occurred to me that the "first place in mathematics" in my class can solve this problem.
Thinking about it, I turned on my computer, logged into QQ and saw Tintin online. I clicked on his QQ to chat with him. "Chicken, I have a math problem. Can you tell me? " After a few seconds, "OK, which way?" Appeared on my computer screen. "It's written on the math test paper ..." I said and sent him the content of the question. "Oh, this way. You use this to remove it first, and then ... do you understand? " "I ... I don't quite understand. Can you say that again? " "yes. Or we can use the equation to define the class as X people ... ""Oh, I see, thank you. " "You're welcome." Knowing this problem, I am like "another village".
Many successful people have said that behind every success, there will always be someone to help and encourage him. For me, that person is him-my good partner, a good partner who is willing to help others.
Math diary, one day in the fourth grade, bitter rivals Zhang Xiaoping and Tan Xiaogang met again in the department store. This time, they didn't come to compete and guess riddles, but to use their brains. This time, Party A (Zhang Xiaoping) asked questions, but because Zhang Xiaoping was nervous (I was scolded once by Tan Xiaogang's crow mouth and lost once last time), I saw Zhang Xiaoping roll his eyes and saw a piggy bank, so I smiled and said confidently, "Oh-oh-oh-ah!" Party B (Tan Xiaogang) accepts questions. Xiaohong has a piggy bank, and all the coins are saved, of which 2 cents is 22 more than 5 cents. In terms of money, 5 cents is 40 cents more than 2 cents. It is known that these coins have 36 1 cent. Q: How much money is there in Xiaohong's piggy bank?
This time, Tan Xiaogang was blindsided and saw stars. He thought for a whole hour. Zhang Xiaoping wandered from the first floor to the 36th floor, and his feet were sore.
Looking at this Tan Xiaogang can finally have today, Zhang Xiaoping's heart is hilarious.
"Come, let me tell you one thing! Twenty-two pence over five pence counts as zero. 02×22=0。 44 yuan, that leaves 2 minutes and 5 minutes. Because five cents is 0 more than the original two cents. 4 yuan, so 5 points is 0 more than 2 points. 44+0。 4=0。 84 yuan. Each nickel is more than 2 cents. 05—0。 02=0。 03 (yuan), so 0. 84 contains 0. The number 03 is the number of nickels: (0. 02×22+0。 4)÷(0。 05—0。 02)=28 (pieces), 28+22=50 (pieces), 0. 05×28+0。 02×50+0。 0 1×36=2。 76 yuan
Math diary, a grade 4 student with 8 children, will think: How many lucky money will I receive this year? How to use it after receiving it, this year may be tuition, this year may be pocket money, and so on. What about me? My mother keeps the lucky money in the bank every year. When I grow up, I will use it if necessary, such as paying expensive tuition. Go on a trip; Buying a house and a car can be sponsored a little, and so on. There are thousands every year, and now it is estimated that there are tens of thousands.
Hope, hope, hope, the day of giving lucky money this year has finally arrived!
"Tintin ..." The doorbell rang and I hurried to open it. At the door stood my little aunt, my sister-in-law's father, aunt, grandpa, grandma, grandpa, grandma … I stood behind them, hammering their backs and rubbing their waists, which was very clever. If I do, maybe they will give me more lucky money, haha!
Today, my mother cooked a sumptuous meal for the guests. What are my favorite dishes, such as salted duck, braised pork, scrambled eggs with tomatoes and so on? After dinner, my mother sent them away. I hurried back to my bedroom and excitedly counted this year's lucky money,100,200,300 ... 900! Huh? Only 1900? I had 20xx last year. Didn't someone send it to me? I'm confused.
At this moment, the doorbell rang again, and it was my uncle who came back! He gave me a red envelope, saying that I had eaten and drunk just now, and I remembered it when I went out, and then I turned around and left.
This year, I added 20xx yuan, which includes the expectations of my elders. As the saying goes, "One hundred dollars grows in the colored thread, and then I put it away from the pillow to discuss the price of firecrackers and flutes, which kept Joule busy all night." This is because the elders hope that we can spend the first year safely. They believe that when evil spirits or years hurt children, children can use the money to bribe them and turn evil into goodness. This is not superstition, but the love of our elders. Therefore, we should study hard, live up to their expectations and live happily every day!
In math diary, it is mom who buys food and pays the bill every day. Today, when I was shopping, I said to my mother, "Mom, we have learned to use money. Let me verify my learning results today! " Mother smiled and nodded.
I saw my mother stop at the place where she bought tomatoes, and I knew she was going to buy tomatoes. I asked my mother in a low voice, "Mom, how many Jin of tomatoes did you buy?" My mother also whispered to me, "Two Jin!" I thought about it, and my brain thought quickly: 2 kg = 1000 g. So, I said to my aunt who sells vegetables, "How much is this tomato?" The aunt who sells vegetables said, "Two and a half dollars, how many pounds do you buy?" I answered her, "Two Jin." When I said it, I thought: 2. 50+2。 50 = 5 (yuan). I took five yuan from my mother and gave it to my aunt.
My mother took me to the place where chicken wings were sold, knowing that she was going to buy chicken wings. I asked my mother inexplicably, "Mom, how many pounds of chicken wings do you buy?"
Mom said, "Buy two chicken wings and one chicken wing 3.5 yuan." I thought to myself, 3. 50+3。 50 = 7 yuan. My mother handed me ten yuan, and I thought about it, knowing that my uncle who sold chicken wings would give me three yuan. I gave the money to my uncle and said, "Buy two chicken wings." Uncle simply said, "All right!" After a while, my uncle really gave me three dollars.
On my way home, I want to know how much money I spent today. So, my little head turned quickly again: from school to the vegetable market next to my home, one person used three pieces, and then three pieces. 00+3。 00 = 6 (yuan). It cost five yuan to buy tomatoes. It cost seven yuan to buy chicken wings. 5。 00+7。 00= 12。 00 (yuan). It cost twelve yuan to buy food. 6。 00+ 12。 00 = 18 (yuan). I spent eighteen dollars today.
It's so interesting to apply the knowledge from books to life!
Math diary, a senior,1February18th, our whole class went to Hongkong for two acting classes, and of course we had to buy tickets.
1 yuan HKD = 1.07 RMB, but if you change at the station, it will become 1 HKD = 1. 1 RMB. How much can I save by changing in the bank? Full Ticket Number: 26 Half Ticket Number: 12 Full Ticket Price: 230 yuan.
Hk (return) 130 hkd (departure) at the station: 130+230=360.
Half price ticket: 1 15 HKD (return to 95 yuan).
In RMB, add195+115 = 200.
One third is 360÷ 10=36 (yuan), and 360+36=396 (yuan).
(yuan) is converted into RMB plus one tenth, that is, 200÷ 10=20 (yuan), 200+20=220 (yuan) is converted into RMB: 130+230=360 yuan) (converted into RMB plus 7,36 × 0.7%) Rmb plus 7×2= 14 (yuan) 200+ 14=2 14 (yuan) 396-385.2= 10.8 (yuan) 280.8+72. The railway station can really make money! 220-214 = 610.8× 26 = 280.8 (yuan) 6× 12 = 72 95+ 15 = 200 (yuan) adults.
People's idea of five yuan Liang Yi's five yuan can do many things in Guangzhou people's mind, such as buying two bottles of canned drinks, buying a box lunch, buying five sets of chess, taking the bus twice ... and even giving others red envelopes during the New Year. But in the eyes of Hong Kong people, he is insignificant and can only buy a bottle of drink or take a bus. Rmb 107 is convertible into Hong Kong dollars 100. The monthly income of Hong Kong people is ten times that of Guangzhou people, which is 3,000 yuan, and that of Hong Kong people is 30,000 yuan. If Hong Kong people spend 5 yuan, it is as easy as Guangzhou people spend 0.5 yuan.
Math diary, fourth grade, 1 1 The four of them have been idle in the sky since they learned the scriptures. I finally look forward to Tang Priest's 5830th birthday. The Tang Priest said, "It's boring to be idle all day! Just right! " Tang Priest shook hands and made peace, ready for a big fight. "Eight quit! Bajie! " Tang Priest shouted. Pig was fast asleep when he woke up and ran to the master and said, "Master, what do you want me to do? Can I help you? " "It's okay I'll call you? What a pig's brain! ! ""Tomorrow is my 5,830th birthday, and I'll take you shopping! Get ready for a big fight. " "The wu is empty! Lao Sha! Come here! ! ""Master, what are you doing? " They all said. "The wu is empty to buy a table and stool! Lao Sha buys bowls and chopsticks. He needs 800 kilograms of spinach, 200 kilograms of peppers, 500 sets of tables, chairs and benches, and 0/0,000 sets of chopsticks. Go ahead and wait for your good news for the teacher! Don't forget to tell me how much each of you spent! "
Bajie buys first: one and a half slices of spinach, one kilogram of gold, two or two peppers and one kilogram of gold;
One gold and a half = 1.5 two gold.
1.5×800= 1200 (2) 2×200=400 (2) 1200+400= 1600 (2)
Bajie spent 1600 two gold to buy grain.
Then there is Wukong: five stools and one table (one table and two stools are a set).
5+10+5 = 20 (2) 20× 500 = 10000 (2) Money was not enough, so Wukong conjured up10000 gold.
8400+ 10000= 18400 (2) 18400-8400= 10000 (2)
Wukong spent 10000 two gold.
Finally, old Mai Sha.
Chopsticks 1 two bowls 5 two bowls (one bowl, two chopsticks as a set)
1+ 1=2 (2) 2+5=7 Liang 7× 1000=7000 Liang.
Lao Sha spent 7000 taels of gold.
"Your situation is known by the teacher. Bajie spends the least money and rewards 5000 taels of gold! " The master said.
Wukong and Lao Sha retorted, "What he bought was the cheapest. It's so unfair! "
Math diary, Grade Four 12 Slowly, mathematics has become a strange word in people's minds. Today, my father gave me a math problem. Let's have a look!
Title: A rectangular aluminum sheet with a length of one meter and twenty centimeters and a width of ninety centimeters can be cut into a disc with a diameter of thirty centimeters. How many pieces can I cut at most?
I think: should we first convert the unit into 120 cm, then multiply it by 90 cm, and then divide it by 30 cm? Or the conversion unit, divided by 30 cm for multiple, and then multiplied by? When these two methods were in a mess in my mind, my mother came to the rescue. I told my mother my two methods respectively. My mother thought for a moment and said, "this topic should be done in your second way." First of all, if you do it in one of your ways, it is 120x and so on. 10800 (square centimeter) 10800÷30=360 (square). The answer should be 360. Why are there so many here? If the second method is used, it should be120 ÷ 30 = 490 ÷ 30 = 33x4 =12 (block), which is more reliable. Secondly, you can find it by drawing. " Mom said that when she saw me, I immediately got a heart, ran to get a piece of paper, pen and ruler, and began to draw. It will be finished soon, a rectangle with 12 squares. Every square has a circle and 12 squares. Finally, it proves that my first method is wrong and my second method is right! My mother suddenly asked me, "Will it be now?" I said loudly, "Yes! ..... "After hearing my fluent way of doing the problem, my mother said," But remember, this is not lip service! " "Be sure to abide by it!" I made a police salute, and my mother couldn't help laughing.
After this math problem, I found that my math is not very good. I must work hard! Be a powerful doctor of mathematics! Come on!
Math diary 13 The second class in the morning of grade four will be an unforgettable math class. If the teacher makes any noise in class, you will be tongue-tied. She is Huang Yue, the famous captain of our class. Be polite. Let's call her "Miss Huang" for the time being.
As soon as the bell rang, I saw "Miss Huang" on the podium, Teacher Feng sat down below and three teachers came to the classroom. Suddenly, a tender voice floated into our ears: "Hello, classmates! My surname is Huang, and everyone will call me' Miss Huang' in the future. " At this time, I found that "Miss Huang" blushed like Guan Gong's face in a TV series. However, I can see that she is trying to control and encourage herself. Gradually, she became calm and active in class.
But it didn't last long. Because "Miss Huang" raised a slightly complicated question, no matter how we think, we can't figure out the answer. "Miss Huang" was so anxious that a cold sweat broke out on his forehead, but it still didn't help. Fortunately, she still used her quick wits and cast a look of help to Teacher Feng. Teacher Feng got the message and gave us a hint. We racked our brains to think again. After a while, the students' little hands were like mushrooms after the rain. At this time, "Miss Huang" told me to get up and answer. Seeing that my answer was correct, she nodded and praised, "You are very clever!" " I don't even want to mention how happy I am, which is sweeter than drinking honey.
As soon as the bell rang, there was thunderous applause in the classroom. I sat in the back and heard the teacher praise her: "This little girl is really not simple, arrogant and flexible. She can not only improvise, but also have strong organizational skills. She will be a teacher in the future. "
Although this class is over, I will never forget, never forget, a flexible and generous "teacher Huang" passed on the fire of knowledge to us.
During the summer vacation in math diary 14, my mother took me to Shanghai to watch the World Expo. My mother told me: "We will take the train from Jiujiang at 8: 10 in the evening and arrive in Shanghai tomorrow 12: 10. My aunt drove back to Jiujiang during the Spring Festival. She started at 8 am and got home at 4 pm that day. Do you know whether the train is fast or the bus is fast? "
I said without hesitation, "To know which is faster, the train or the bus, is to ask their respective speeds. If you want speed, you must know the distance and time. How far is it from Jiujiang to Shanghai? " Mother shook her head slightly and said, "The distance between Jiujiang and Shanghai is 952 kilometers." "I know. First, make clear the train running time at night:12:10-8:10 = 4 (hours), the total train time: 4+ 12= 16 (hours), and the train speed = 952.
4: 00 p.m. =16: 00 p.m. Car time: 16: 00-8: 00 = 8 (hours)
Vehicle speed =952÷8= 1 19 (km/h) because119 > 60, so the car is faster than the train. Mom, did I answer perfectly? ! "
Mom said, "Your final result is correct, but you didn't analyze the topic carefully, but just applied the formula mechanically." . When doing problems and considering problems, we should comprehensively consider all known conditions and open up new ideas. Like the question just now, it is actually the same as the distance. After a long time, the speed will slow down, that is to say, the dividend is constant, and the larger the divisor, the smaller the quotient. Trains take a long time and are slow, while cars take a short time and are fast. "
I was inspired by this.
Math diary, Grade Four 15 There is mathematics everywhere in our life, and everything can't be separated from it.
Today, I happily followed my mother to Yonghui Supermarket. Signs of "buy one get one free", "20% discount" and "buy a box to reduce 5 yuan" are hung at the entrance of the supermarket.
As soon as I entered the supermarket, the goods in front of me were dazzling, and every aisle of the store was crowded with people. You can only go with the flow and walk while watching the goods. Far away, I saw a sign hanging high in front of me, which said "10% off". A closer look shows that my mother is my favorite milk. The price above is 68 yuan, but here comes the problem. I raised my voice and asked my mother, "How much is a 10% discount?" My mother leaned close to my ear and said, "The original price multiplied by 0.9 equals the current price". And the original price minus the original price multiplied by 0. 1 equals the current price. For example, the original price 100 yuan, 10% discount. Then give me a discount at the current price of 90 yuan. Today, I happily followed my mother to Yonghui Supermarket. Signs of "buy one get one free", "20% discount" and "buy a box to reduce 5 yuan" are hung at the entrance of the supermarket. Ten yuan. "After listening to my mother's explanation, I suddenly realized that I had come to the candy section to buy it. I saw the sign that the second piece was half price. I excitedly took my mother's hand and said, "mom, this second box of chocolates is half price." It's too cheap. Buy it quickly! " Mom said jokingly, "Do you know how much it costs to buy four boxes?" I confidently replied: "The original price is 30 yuan a box, and a box of four boxes costs 90 yuan." Mother nodded with relief. I am glad that I can learn math knowledge by visiting the supermarket.
There is mathematics everywhere in life. As long as you pay attention to it, you can find it!