On a sunny weekend, I went shopping with my parents. "ah! The shopping mall is really big! " I can't help admiring. I came to the toy store first. The dolls here are really small and cute. Suddenly, I found some very strange shapes. I flew like an arrow with a hedge line. There is a dazzling array of things, and various shapes emerge in front of my eyes. At this time, my father pointed to the figure and asked me, "What kind of figure is this?" I said eagerly, "It's a cuboid!" Dad asked again, "Do you know the calculation formula of cuboid?" I frowned and thought for a long time, but I still didn't know anything. At this moment, a clear and bright voice echoed in my ear. It turned out to be my mother. Mother said softly, "the volume formula of a cuboid is very simple." Just use length x width x height. Give me an example. You see, if V is used to represent the volume of a cuboid, then A, B and H are used to represent the length, width and height of the cuboid respectively. The above formula can be written as: v=abh. " As soon as my mother's words fell, I suddenly realized, "Oh, I see, the volume formula of a cuboid is the same as that of a cylinder, both of which are length × width × height." "My baby daughter finally understands that she must think independently and do the problem seriously." Her mother couldn't help crying when she said this. This day's shopping made me understand a lot of truth.
2. math diary 500 words in the fifth grade of primary school.
On Sunday, my mother bought me a fashionable sportswear and a pair of Nike shoes in the mall. When I got home, my father asked, "How much did you buy these clothes, pants and shoes?" I immediately came up with an idea to play a trick on my father, because I knew that my father sometimes didn't speak as fast as me. So I stamped the price tag and said, "I'll call you!" " If you can't figure it out, I'll let you buy me a better suit of clothes and shoes. "Dad said," Then have a try. " "The price of clothes is twice that of 500, minus 600 plus 100, and then the sum of 2 is the price of clothes. Pants are three times 700 minus 1900, and shoes are three times 400 minus 4 plus 200. How much did it cost? " Dad's head suddenly got bigger, so he said, "What is this? Addition, subtraction, multiplication and division. I can't figure it out. " "Well, buy me new clothes!" "No, I haven't answered the answer yet." "Well, you listen up. (500×2-600+ 100)÷2=250 yuan, 700×3- 1900=200 yuan, 400×3÷4+200=500 yuan total * * * 250+200+5000. Dad said, "Wow, that's what it is. All right, I'll give you new clothes. "Yes, I won this round, Dad.
It turns out that many things in life can be solved by mathematics. I will continue to discover mathematics in my life and learn more calculation methods.
3. math diary 500 words in the fifth grade of primary school.
At noon that day, I was alone at home, and suddenly I was hungry, so I went to the supermarket downstairs to buy snacks. When I arrived at the supermarket, I bought two boxes of pickled noodles, three chicken legs and five packs of quail eggs. My aunt at the supermarket gave me 14.6 yuan when I checked out. Walking home after paying the bill always feels that something is wrong. So I calculated in my mind: 6 yuan paid a box of pickled noodles in Laotan, and bought two boxes of pickled noodles, which is 12 yuan. Chicken legs for each 6 yuan, I bought three * * * yes 18 yuan; Quail eggs 1.8 yuan 1 bag, bought 3 bags * * * 5.4 yuan; So 12+ 18+5.4=35.4 yuan, and I just paid 5 1 yuan, and 5 1 yuan minus 35.4 yuan is equal to 15.6 yuan. Oh, that aunt made a mistake just now. She gave me change of 1 yuan. I was really careless. I must get rid of this bad habit in the future!
So, I turned and ran quickly to the supermarket and panted to my aunt in the supermarket: "Aunt, you have miscalculated the money. You owe me 1 yuan less, it should be 15.6 yuan! " Aunt frowned and said, "Right?" "I paid you 50 yuan, but later I found a 1 in my pocket, so I paid you!" I will explain quickly. "Oh ..." Aunt suddenly realized: "Sorry, little friend, I have miscalculated." Aunt said as she handed me the money. "It doesn't matter, thank you, aunt. Goodbye! " After receiving my aunt's money, I went home happily with snacks.
I remember it clearly. What the teacher said is true. Mathematics is everywhere in our daily life. It is really useful to learn it well!
4. math diary 500 words in the fifth grade of primary school.
At noon, my father came back from work, humming a ditty, and happily stepped into the house. I greeted him and asked, "Dad, what's so happy today?" My father said, "I got a raise this month." I asked, "How much salary do you get now?" Father thought for a moment, smiled and said, "I am higher than my salary." Our monthly salary adds up to 2800, and the monthly salary difference is 100. How much do you think I get a month? " After listening to my father's words, I began to draw line drawings on paper to help me understand:
Through observation and thinking, I quickly worked out the answer and told my father. First of all, mom's salary is as much as dad's, so mom and dad's monthly salary is (2800+ 100)=2900 yuan, and then the total monthly salary is divided into two parts, and 1 part is dad's monthly salary. The formula is: (2800+ 100)÷2= 1450 yuan.
Dad listened and nodded with satisfaction. At this time, my mother, who was cooking, said to me, "Do you have any other methods?" "There are other ways." I'm surprised. I stopped to observe and think curiously. I found that the key to this problem is to find out who is the standard. Different standards have different methods. So, I have a second method: taking mom's salary as the standard, assuming mom and dad's salary is the same, then the sum of their monthly salary is (2800- 100)=2700 yuan, and then divide the sum of monthly salary into two parts on average. 1 part is mom's monthly salary, and finally it is more than mom's 100. The formula is (2800-100) ÷ 2+100 =1450 yuan.
After listening to the second method I introduced, mom and dad both laughed. ...
5. math diary 500 words in the fifth grade of primary school.
At noon today, I was doing my math summer homework. I wrote and wrote, but unfortunately I met a very difficult problem. I've thought about it for a long time, and I can't figure out why. The problem is this: there is a cuboid, the product of the front and the upper two areas is 209 square centimeters, and its 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 scratched my head, a colleague of my mother came for a long time. 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.
The final result is 374 cubic centimeters. My formula is: 209 =11919 = 2+11× 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.