Math diary 1
On Sunday, Yang Wen and I played 2 1 point. The rules of the game are simple: everyone draws four cards respectively, and then uses these calculation methods of "+,-,×, ⊙", and the final number must be 24.
The game started, and we each drew four cards. Alas! How come my cards are so bad! Listen, four people are all trump cards. At this moment, I only heard Yang Wen say, "I can do it. You see, 5+5= 10, 10×2=20, 20+4=24. " I lost the first round. But I am not discouraged, because there are still opportunities in the future, and I must seize them and strive for them. I drew four more cards "6, 5, 8, 3". I was so excited that I blurted out immediately: "6-5= 1, 8× 3 = 24,24 ÷1= 24. Now 1 is even with 1. "
Yang Wen said, "Anyway, I will definitely beat you in the next round." The third round arrived, and I drew four more cards "10, 9, 6, 10". I was dumbfounded at first sight. Suddenly, Yang Wen shouted: "6× 4 = 24,24+1-1= 24. 2 1 I won. " I watched him smug and helpless.
Although I lost the game, I think 24 o'clock is really interesting and math is really wonderful. I must study math well in the future and use the mixed operation of "+,-,×, ⊙" flexibly. In the next 2 1 point game, I must skillfully use it and become a master.
Math diary 2
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.
Math diary 3
On Saturday, my mother and I went to our hometown in the country. Along the way, I saw farmers' uncles harvesting sweet potatoes. They smile at the farmer's uncle like fat dolls. My mother told me, "It's sweet potato harvest season", and then she said to herself, "Today, sweet potatoes are rich again." I said, "What's the use of collecting so many sweet potatoes?" Mom said: "Sweet potato can play a great role! Can be made into sweet potato skin, sweet potato powder, sweet potato strips ... "
Knowing that I had learned the percentage, my mother asked me: 50 Jin of sweet potato can squeeze out 5 Jin of sweet potato powder. What is the flour yield of these sweet potatoes? If grandma squeezes 500 Jin of sweet potatoes this year, how much sweet potato powder can grandma collect? I calculated:
5/50× 100%=0. 1× 100%= 10%
500× 10%=50 (kg)
After I finished the calculation, I said to my mother, "The output of sweet potato powder is 10%, and grandma can receive 50 Jin of sweet potato powder this year." I asked my mother curiously, "What does Grandma do with so much sweet potato powder?" Grandma said, "Our special snack in Pingtan-salty rice is indispensable. Our family of three needs 0.4 Jin of sweet potato flour for a salty rice meal. Then grandma gave us 10 Jin, so how many times can we cook salty rice? " I calculated:
10÷0.4=25 (times)
I said to my mother, "I can do it 25 times." Mom said: "Eat salty rice twice a month on average, is it enough for one year?" I said, "I can't finish it yet. I can add another meal during the Chinese New Year. " Mom said, "You are really good. In fact, it can also be made into vermicelli soup, vermicelli and vermicelli knot. "
Math diary 4
This morning, I finished my homework and prepared to go out. At this time, my father came over and asked me with a smile: "Son, let me ask you, have you learned to weigh?" "Of course I do!" I answered loudly.
"Well, let me test you." So, dad said, and drew a picture on the paper. Dad said to me, "The actual length of this part is 5 mm, and the distance on the drawing is 10 cm. What do you think is the scale of this painting? " "That's not easy? 10 cm = 100 mm, 5: 100 = 1: 20, "I blurted out at the scale of this picture. Dad smiled and said, "Right?" Think about it, what is the meaning of scale? I thought about it and said, "The scale represents the ratio of the distance on the map to the actual distance." "Is that what you want to ask?" Dad asked.
I suddenly realized and said, "I know what's going on. I have calculated the ratio of the actual distance to the distance on the map. " The distance of parts on the drawing is 100 mm, the actual distance is 5 mm, and the scale is 20: 1. "
"That's right!" This is a special scale, which is greater than the previous term and the latter term. The simplified latter term is generally 1. This ratio should be used after the actual object is enlarged. "Son, you can correct your mistakes in time. I am proud of you. "
I am very happy to hear my father's praise.
Math diary 5
In the evening, I saw a problem in the Olympiad Book: the number of apple trees in the orchard is three times that of pear trees. Master Lao Wang fertilizes 50 apple trees and 20 pear trees every day. A few days later, all the pear trees were fertilized, but the remaining 80 apple trees were not fertilized. Excuse me: How many apple trees and pear trees are there in the orchard?
I am not intimidated by this question, but it can stimulate my interest. I think the apple tree is three times as big as the pear tree. If two kinds of trees are to be fertilized on the same day, Master Lao Wang will fertilize "20×3" apple trees and 20 pear trees every day. In fact, he only fertilizes 50 apple trees every day, which is 10, and the last 80 trees. Therefore, Master Lao Wang has been fertilizing for 8 days. 20 pear trees a day, 8 days is 160 pear trees. According to the first condition, there are 480 apple trees. This is to solve the problem with the idea of hypothesis, so I think the hypothesis method is really a good way to solve the problem.
Math diary 6
This winter vacation, I'm going to Beijing to take part in the competition. As time was tight, we decided to go by plane. But the full-price ticket for Urumqi-Beijing flight is 24 10 yuan/ticket, which is too expensive. My father and I decided to order discounted air tickets online. There are many factors that affect the discount of air tickets, such as itinerary, booking time, group booking, off-season, etc. But the most important factor is the booking time. The earlier the discount, the cheaper the price. We decided to book tickets in advance!
Because mom and dad are both members of China Southern Airlines, I used mileage points to exchange air tickets first, but after checking, I found that there was no exchange ticket before 14, so I booked a return ticket for 19 first. Originally, we could change a return ticket from Beijing every 65,438+05,000 kilometers, but with 65,438+0000 kilometers, we can take a high-end economy class, so it's a bit extravagant. We exchanged 48,000 kilometers for three tickets without paying!
After our online search, February 12 is the cheapest, with a 4.5% discount. In this way, the air ticket of our family changed from the full price of 7230 yuan to 3250 yuan. In this way, our round-trip air ticket to Beijing only needs 3250 yuan, which is cheaper than the normal full price 14460 yuan112/0 yuan. What a good deal!
We can reduce the cost through discounts, integral exchange, etc., and we can also use the mathematical operations we have learned, such as addition, subtraction, multiplication and division. Mathematics is really everywhere!
Math diary 7
There is a problem in today's math homework to weigh a pair of shoes. So I went to my mother and asked for a scale. Mom said she didn't have weighing scale. What shall we do? However, as the saying goes, "Nothing is difficult in the world". I think there must be a way. So, I used my clever brain and came up with a homemade balance.
I cut off the paper covers of the empty moon cake box piece by piece, brought transparent folding tape, folded one of the paper covers into a regular triangle and put it on the table. Another piece of paper is made into the left and right disks of the balance and placed on the triangle in a balanced way. Then find something with weight at home as a weight. For example, my mother bought toothpaste, lipstick and other items, including 120g, 40g, 18g, 3g. I'm very excited to say that the shoe activity has started. I put the shoes on the left side of the homemade balance and the "weight of goods" on the right side. It is best to balance the weight on both sides. Then the sum of the weights is the weight of my shoes. Exactly 86 grams. Hard work pays off! I finally finished my math homework. Mom praised me when she found out.
He also joked with me: "In ancient times, there was a clever Cao Chong as an elephant, but now there is a clever Han Han as a shoe!" Say that finish, everyone laughed. It turns out that there are scales everywhere in life!
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