Math diary, the first volume, grade four.

Today, my mother watched Lucky 52 on TV, and there was a question in it. The primary school students didn't get the doctor's answer correctly. My mother asked me to do it. The topic was: A monkey moves corn, carrying 12 bags every day and eating 7 bags at night. When can this monkey move 5 bales of corn? Answer A:99 days. Answer B1 days. Answer C:11 days. < P > I think: 12-7=5 bales, that is to say, 5 bales a day. So, 5÷5=1 (days). < P > Suddenly, I was laughing in my heart. So it took 1-1=99 days, and I handed in my "paper" at my mother's place. My mother said, "Congratulations, that's right. Wow, I'm smarter than my doctor.

Shopping

Today is the weekend. In the afternoon, I went shopping with my grandparents.

When we walked into the Jeanswest store, Grandma selected three T-shirts from 29 yuan and prepared to buy them. Grandma asked me, "How much is this * * *?" Without thinking, I said, "One * * 87 yuan (29×3 is about 9, 9-3× 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." Walking into the rice noodle shop, we bought a bowl of medium rice noodles, two bowls of small portions, one steamed dumpling and two bowls of porridge. Grandma asked me, "How much should I pay?" I said, "One * * 17 yuan, because the middle portion is 4.5 yuan, the small portion is 3.5 yuan, the steamed dumplings are 3.5 yuan, and the porridge is 1 yuan (4.5+3.5× 3+1× 2 = 17 yuan)."

after eating, we went home.

Buy oranges

In life, there is mathematics everywhere. For example: buy food! Buy stationery! Measuring cloth, etc., all need to use mathematics.

this semester, the teacher taught a new knowledge, which is multiplication and division of decimals. This knowledge has helped me a lot!

Last night, my mother went to buy oranges. A kilo of oranges is 1.8 yuan's, and my mother bought 4.5 kilos. I should have paid 8.1 yuan. However, the shop assistant was careless and didn't know how to calculate it, so it became 9 yuan money. Fortunately, I made use of my knowledge of Protestantism this semester and calculated in my mind that 1.8/2 = 9 (angle) 1.8x4＝7.2 (yuan) 9 (angle) +7.2 yuan = 8.1 yuan, which immediately corrected the mistake of the shop assistant.

Not only did my aunt, the shop assistant, praise me for my cleverness and my ability to multiply and divide decimals in such a small city, but on my way home, my mother also praised me for saving her .9 yuan, and the knowledge I learned can be applied flexibly in my life.

yes! If you don't learn this math well, you will lose not only this .9 yuan, but also hundreds, thousands or even hundreds of millions.

when can the snail climb out of the well?

Today, I read a thinking question in a book:

A snail is trapped in a well, the depth of which is 15m. The snail climbs 1m every day and falls 3cm in the middle of the night. When can the snail climb out of the well?

I listed the formula on the draft paper: snails climb 1-3 = 7cm every day, snails climb 7× 1 = 7cm in 1 days, snails climb 7× 2 = 14cm in 2 days, and snails have 15-14 = 1cm = 1m on the 21st day. It takes 2+1=21 days for a snail to climb out of the well.

It turns out that there is mathematics everywhere in life!

It's sunny on Sunday, September 9th

What is mathematics

Today, I heard a story from my grandmother.

This is the true story of the famous Polish mathematician Serpinski.

One day, when he was moving, his wife took out his luggage and said to him, "I'll call a taxi, and you keep an eye on the luggage here, ***1 boxes." After a while, his wife came back. He said to her, "Just now you said there were 1 more boxes, but I counted only 9." "No, it must be 1." "What to say, I count again, , 1, 2, 3. . . . . 。”

oh, I see, mathematics is made up of , 1, 2, 3, 4, 5, 6, 7, 8, 9.

September 9, 27

Understanding of the corner

In our life, we can touch things related to mathematics everywhere.

Take horns as an example. You can find many things related to horns as long as you observe them carefully. For example, we often see a clock. At 12: 3 noon, I found a straight angle on the clock face. If it takes another 1 minutes, an obtuse angle will appear. If it takes another 5 minutes, that is, at 12: 45, a right angle will appear. When the pointer is walking for 15 minutes, that is, at 1 o'clock, an acute angle will appear on the clock face.

I listened to it, and after reading it, my heart was full of joy. I want to learn math well and apply what I have learned to my present life.

the story of the decimal point

although the head of the decimal point is small, I know that the decimal point is not small.

for example, 3.8 yuan, without the decimal point, doesn't it become 38 yuan? What a difference between 3.8 yuan and 38 yuan! Such a comparison, don't you see how big the decimal point is?

Many students often leave it out when writing, so this number is not the one you originally wanted to write. So let's not make this big mistake again!

Eat sugar

Today, my mother bought some sugar. I couldn't wait to eat two-fifths of it first. Then, I took a sip of water and went to do my homework. After I finished my Chinese preview homework and math exercise book, I ate another fifth. Then my mother said, "What kind of sugar is so greedy?" I'll have some, too. "In this way, we ate four-fifths of the sugar, and my mother asked me," How much sugar is left? " I replied, "There is only one fifth of the sugar!" On this day, I used math knowledge to express the sugar we ate. I am really happy now.