In the morning, when I finished writing my composition, my father asked me, "Li Ran, did you finish your homework so soon?" Let me ask you some math questions. "I said confidently," Good! " "The area of a blackboard is about 400 ()?" "The area of a blackboard is about 400 square decimeters. ""The area of that playground is about 2500 square meters? I was dumbfounded: "Fang ... decimeter." Dad smiled and said, "Think again. "I thought for a moment: a blackboard is about 400 square decimeters, and 2500 is about six times that of 400. Ah, how can a playground be as big as six blackboards? " The area of the playground should be 2500 square meters. ""not bad. " Dad smiled and said, "Then how do you know?" "I compared it with the fast blackboard." "That's a good idea. Let me ask you one more question. Is this table 45 () wide? " "This table is 45 centimeters wide. "
After answering the question, my father said, "I haven't mastered the area unit yet!" " "I bowed my head in shame.
Today is the weekend. In the afternoon, my grandparents and I went shopping.
We walked into the Jeanswest store, and grandma chose three T-shirts made in 29 yuan and bought them. Grandma asked me, "How much is this * * *?" Without thinking, I said, "A * * 87 yuan (29×3 is about 90,90-3×1= 87 yuan)."
After grandma bought clothes, we walked out of the clothing store. Grandma said, "It's already half past five. Let's eat rice noodles. " Into the rice noodle shop, we bought a bowl of medium rice noodles, two bowls of small portions, a steamed dumpling and two bowls of porridge. Grandma asked me, "How much should I pay?" I said, "One *** 17 yuan, because the share is 4. 50 yuan, the small portion is 3. 50 yuan, 3 steamed dumplings. 50 yuan, porridge is 1 yuan (4. 50+3。 5× 3+ 1× 2 = 17 yuan).
After dinner, we went home.
Math diary's fourth grade 3 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.
Once I took a math test and really realized the importance of 0. When the exam was handed out, I got 99 points! I made a mistake at once. The result is 450-90. "How could I make a mistake with such a simple question?" I muttered to myself. I remember when I was dictating 450÷90, I easily wrote down 50, and I was still confident, but in the end it turned out to be 5, with an extra 0. This is very inappropriate! What should not be wrong is also wrong. Think about how important 0 is!
If I became the financial general manager of the company in the future and someone else came to withdraw money, I would have taken 1 million yuan, but I was missing a 0, which was written as 1 million yuan, and I also wrote 1 million yuan on the bill. Then who should I ask for this 900 thousand?
Math diary Grade Four: It's winter, and the little squirrel has to prepare food for the winter.
One day, the little squirrel came to the forest with a big bag on his back and said to Grandpa Pine, Would you please give me your pine cone? Grandpa Pine was generous and said: Pick as many as you want. The little squirrel is very happy. He picked it up and sang. Soon the bag will be full. Grandpa Pine asked: How many did you pick? The little squirrel said, Oh, I forgot! Grandpa Pine smiled and said, "I planted 16 pinecones, and there are nine more. If you can figure out how much you picked, I'll let you carry it. " The little pine tree is in a hurry and can't be counted. What shall we do? If Grandpa Pine won't let him take it away, what will he eat in winter? I will help it.
In math class, the teacher said: knowing the total number and finding the partial number is to remove the known partial number from the total number and get another partial number, which is calculated by subtraction. I soon figured it out that the little squirrel picked 16-9=7 (pieces).
Math diary, Grade Four and Five Today, I had a math class with great interest ―― moving the decimal point to the right.
Although the decimal point is called "small", it is extremely difficult to jump. If the decimal point of a number is shifted to the right by 1 digit, 2 digits and 3 digits respectively, the' number is 10 times, 100 times and 1000 times the original number respectively. ......
By analogy, the decimal point of a number is shifted to the left by one, two and three places respectively ... and the numbers obtained are one tenth, one hundredth and one thousandth of the original number respectively. ......
Please remember that although the decimal point is small, it has great skills. As long as he stretches and moves, those numbers will get bigger and smaller.
Math diary, Grade Four and Six, today, we did oral arithmetic acceptance. In the second class, after Mr. Dong entered the classroom, the noisy classroom suddenly became so quiet that even the needles could be heard.
Time is pressing, I know I need to hurry, finish the problem quickly, and then check. The students all spend time doing oral calculations. In just three minutes, time passed slowly. Listening to Teacher Dong's "Stop", the team leader quickly and quietly handed the paper to Teacher Dong.
In the afternoon, I heard Wang Zicheng say, "Yongjiawei got 96 points." I thought, "What's the matter? Let me see! " Alas! There are several simple questions I did wrong, and I really shouldn't do them. I regret it very much My mother usually asked me to do oral calculations, but I didn't, and the consequences were very serious!
Mr. Dong informed me that there are only ten days left before1February 2 1 day. I want to seize the precious time, practice oral calculation more, get a good grade in the exam, and go home to surprise my grandmother.
Math diary, fourth grade, on July 6th, it was sunny on Wednesday.
Since the sixth grade, I really haven't encountered too difficult math problems, but recently, I have racked my brains to come up with a formula to solve them!
The title of this difficult problem is: a pasture where grass grows at an average speed every day. The pasture can feed 15 cows for 20 days or 10 cows for 20 days. So, how many cows can eat the grass growing on this pasture every day?
I have been studying for a long time. How much grass does the Yi people in A Niu eat? I don't know how many catties and baskets there are. What should I do? Suddenly, I had an epiphany, and I had it! No matter how much you can eat, assuming it is a unit, it will not be solved. Assuming that the amount of grass a cow eats every day is 1, it can be calculated that the amount of grass that15× 20×1= 300,300 is the original amount of grass in this pasture plus the new amount of grass in these 20 days. It can also be calculated that the amount of grass eaten by 20 cows 10 day is 10×20× 1=200.
However, after finding these, how to calculate them? I thought hard and finally found a way: 300-200= 100. Isn't this 100 the difference between grass that grows 20 days and grass that grows 10 days, that is, grass that grows 10 days is 100, that is, grass that grows every day by my sister is: (33
The amount of grass a cow eats every day is 1, so the newly grown grass can feed 10 cows every day.
Through hard thinking, I got the right question, my heart was as sweet as honey, and my efforts finally paid off!
Chapter 8, Grade Four, math diary We have just learned the understanding of large numbers in Unit 1, but I am a little at a loss about the size of 100 million. Today I'm going to explore how big 100 million is.
I want to calculate how many liters there are in 100 million drops of water. I took an injection first and sucked 2 ml of water, drop by drop. There are 60 drops in 2ml water, so there are 30 drops in 1ml water. I calculated again that 100 million drops of water actually have 3333333 milliliters. That means a total of 3333 liters. 100 million drops of water actually merged into 3333 liters of water, which can hold four waterwheels. How big is this number! It seems that we should save every drop of water in our life.
Mathematics is a wonderful subject, with more emphasis on data processing and manual exercises. Math diary can also be written from this aspect.
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, which is a simple addition and subtraction algorithm. 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 counted as 800 plus, and 29 can be counted as 300. One adds 4 and the other adds 5, so the formula becomes 800+300-4-5= 109 1. Look, how convenient it is!
After learning the simple algorithm of addition, learning the simple algorithm of subtraction will be much easier. 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!