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. ...

2. math diary 500 words in the fifth grade of primary school.

Today is mom's birthday. Mom went to work in the morning and didn't come back until evening. At 8 o'clock in the evening, my mother came back. While eating the cake, my mother said to me, "Mom will test you. If you answer correctly, you can eat a piece of cake, ok? " I said "no problem" and began to answer questions. My mother gave the first question: My mother is 36 years old, and you are 10 years old. My mother is several years older than you, and my grandmother is six times older than you. How old is my grandmother? I worked out the result quickly. I said, "My mother is 26 years older than me, and my grandmother is 60 years old this year. It's too simple, my cake will be eaten. " Mom smiled and said, "You are proud." Let's ask another question: Xiaoming is 8 years old and his father is 40 years old. In a few years, Dad will be twice as old as Xiaoming. Now I'm silly, thinking hard, as if my cake can't be eaten. Mom said, "How's it going?" "Let me think again, I can't figure out that I don't eat cake."

After a while, I thought of a stupid way. I found out their ages. After a year, Dad and Xiaoming are one year older. I finally figured it out. Twenty-four years later, my father is just twice as old as Xiao Ming. I told my mother the idea. My mother said there was an easier way, and then she told me. Just subtract Xiao Ming's age from his father's age, and a few years will be Xiao Ming's age, that is, 32 years, and then 32-8=24 years will be the past years. I suddenly realized that things could have been so simple.

Mom said: it's good to find a way to get the result by yourself. As a reward, I eat cake. I am both happy and embarrassed. I can't be proud in the future, and children should not learn from me.

3. math diary 500 words in the fifth grade of primary school.

There are two public classes this semester, one is information class and the other is math class. What I like best is the open math class, because Teacher Lu can always teach us interesting knowledge and create a relaxed environment. My heart was pounding when the bell rang. When Mr. Lu put the bucket and cup on the podium, he looked at our curious expression and said with a smile, "This bucket of ink and cup is still for display and is an important tool for this class." After listening to Lu Du's words, the students all sat up straight. Suddenly the classroom was very quiet and only a little noise was heard. The students are waiting to land, and the teacher gives us lessons with his props.

I saw Teacher Lu show us the scale of the bucket. Teacher Lu also asked us to guess how many liters of ink there were. We all sat and guessed, and I thought, this must be more than 2 liters, but it must be less than 3 liters. After almost a minute or two, Teacher Lu announced the answer. He said it was 3.4 liters. Many students in our class clap their hands to encourage themselves. Then Teacher Lu asked another question: Please guess what 1ml is? Some students said, "It should be1mm."

But teacher Lu's words surprised us. Teacher Lu said with a smile, "Actually, 1ml is equal to 0.7mm, so let's get to the point." Teacher Lu first taught us the conversion: 1 liter = 1000 ml, and rising to ml is the carry of three zeros ... Teacher Lu taught us the capacity unit ml with a cup and the capacity unit liter with a bucket, and the students were very happy to learn!

This class is spent in our laughter. After class, the students said, "Today's math class is really interesting!" "

4. math diary 500 words in the fifth grade of primary school.

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.

5. 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.