If you add an inconspicuous decimal point to the middle point of "123", it will become "1.23" or "12.3". If you add an inconspicuous decimal point to "456", it will also become "4.56" or "45.6" ... The decimal point is such a magical symbol that can make all numbers "tiny"!

Unit 7, we learned the multiplication and division of decimals, which made me feel deeply!

The first point: when the lines are vertical, the numbers should be aligned. When column multiplication is vertical, many students often mistakenly think that integers are aligned with integers and decimals are aligned with decimals. If you do that, it's all wet! The correct method should be this: No matter where the decimal point is, when the column is vertical, the ends of the two numbers must be aligned. Only the results and answers calculated in this way are correct!

The second point: Never point the decimal point in the process of vertical column. This is a common problem of many students. When you click the decimal point in the exam, you will be deducted, and you will regret it!

Number three: Be careful. Multiply a decimal by 10, 100, 1000 ... or divide a decimal by 10, 100, 1000 ... Never make a mistake about the position and direction of the decimal point!

Let's study math seriously! There are still many secrets waiting for us to explore in the kingdom of decimals!

1, the application of mathematics is sunny on Friday.

In life, mathematics is everywhere. For example: buy food! Buy stationery! Measuring cloth, etc. , all need to use mathematics. This semester, the teacher taught a new knowledge, that is, the multiplication and division of decimals. This knowledge helps me a lot!

Last night, my mother went to buy oranges together. A kilo of oranges 1.8 yuan. My mother bought 4.5 kg and should pay 8. 1 yuan. but

Careless, I don't know how to calculate, and it's 9 yuan. Fortunately, I used the knowledge of Protestantism this semester. After doing a calculation in my mind, I corrected it immediately.

This mistake.

not only

My aunt praised me for being smart, and I can multiply and divide decimals in such a small city. On my way home, my mother also praised me for saving her 0.9 yuan, and the knowledge I learned can be applied in my life. Yes! If you don't learn this math well, it's not only 0.9 yuan that will lose, but also hundreds, thousands or even hundreds of millions!

On Sunday morning, my grandfather and I went to the pharmacy in the lotus pond and bought two boxes of pills-two boxes of Weiershu, one box of 44 yuan and one box of 22 yuan. Grandpa gave her 50 yuan, and the clerk gave it to Grandpa 6 yuan. When I found the money, I added it up with decimal numbers.

I did some accounting work. Grandpa can also pay like this: 1. Give it to 40 yuan, the shop assistant, and then pay 5 yuan. The asking price is 1 yuan. 2. If Grandpa has change, he can pay 40 yuan first and then 4 yuan. By buying medicine with grandpa this time, I know that mathematics is closely related to our lives.

On Sunday, my sister and I went shopping in the supermarket. I bought a pack.

A bottle of milk and a bottle of soda, a * * * cost 10 yuan.

Bought a box of biscuits and a bottle of soda, and a ***9 yuan money. We gave the shopkeeper 20 yuan money. The shopkeeper gave us money from 2 yuan, and when we were ready to go home,

I also want to buy 10 capsules.

. "I took out the money and found that the shopkeeper gave me 1 yuan. Let's go back and return the extra 1 yuan to him. The shopkeeper praised us as an honest boy, and our hearts were filled with joy.

Yesterday, I got 95 points in the math exam. I made a mistake in filling in the blanks and writing questions. The teacher reviewed the fill-in-the-blank questions for us before the exam. I didn't recite it carefully, but I remembered it carefully. I was thinking about something else when I recited it, and I didn't remember it at all. So, when I took the exam, I couldn't remember it anyway, so

Write clearly a "size". I didn't see the meaning of the title clearly, and it was wrong to write "X" as "⊙". This grade, the first 1 question is because my attitude is not correct, and the second question is because I didn't review it carefully. I will definitely do these two things in the future, but I can't be careless. Teacher, I can't get satisfactory results in every exam. Ever since I went to bed

Then I understood that the most important thing in learning mathematics is understanding. It's no use just copying other people's answers. It's no use copying them. So I will listen carefully in the future and strive for excellent results.

Recently, our students from grade three to grade six took a math test. I only got 92.5 points in this exam. Carelessness made me do a lot. You're right. It's not that I can't. It was careless. There are often some size problems. Without these problems, I would be better. There is a saying: "The first mistake may be excusable, but the second mistake shows that you are a' fool'." Maybe I am this "idiot". My grades are like an olive. Olives hang on the edge of the cliff. If you are not careful,

Will "bump ..." Fall. Achievement depends not on thinking high, but on hard work. An ideal without action is a fantasy. just as

As said, the value of a thing sometimes depends not on people's income, but on people's efforts-on how much you have paid for it. This sentence is correct. Wisdom does not lie in profound knowledge. We can't know everything. Wisdom lies not in knowing as much as possible, but in knowing what we need most and what we don't need to know. Through this exam, I not only tested what I have learned recently, but also exposed many shortcomings of myself, so that I can correct them in time in my future study.

After this test, I found that I didn't make a careless mistake, but I was not so serious. Question 7 in the fill-in-the-blank is a special part of the book.

Don't look carefully; There is another problem in the third part of the third question because I don't look at the problem carefully and think I won't.

And wrong; exist

I shouldn't be wrong. I should know all those questions. Just because of the wrong idea in my mind, I think this question is too simple, so I chose the wrong one. Not only did I make mistakes in exams, but I also had many problems in my daily life. For example, when I write, I often make careless mistakes and write wrong words. Later, I checked and found that it is often the easiest to be sloppy when doing homework and playing for a while.

, there was an error. But now I've changed.

I believe that I will become better after I get rid of other problems.

We had a monthly exam a few days ago. I was very nervous after I finished my math exam, and I was worried that I would not do well in the exam! The results came out yesterday, and I can't wait to know my own results. At 95 minutes, I finally breathed a sigh of relief. I finally put down a heavy stone. After the papers were handed out, I carefully analyzed the reasons for the mistakes as before. I sighed deeply and said, "Ah, I shouldn't be wrong in the two questions, and I believe in myself. I will definitely get 100." However, I am so careless, as if I were going to make a few mistakes! I think: I must remember this lesson and let it remind me at all times that I will not be so careless in the next exam, and I must get the best "100"! From this math monthly exam, I understand that no matter what I do, I must believe in myself and be a confident and good student.

6. Today is Friday, and the test paper has been handed out. When I saw the results, I couldn't believe my eyes, only 86 points short. I am really ashamed and envious to see that others got a score of 100. I wish I could get a score of 100. But I blame myself for being careless, and I also blame myself for suddenly having a stomachache before I finished checking the first half of the test paper. I really don't know what happened. And I clearly found a problem wrong, but I didn't have time to correct it. The question is 4 points. If I add up the scores of this question, I can get 90 points. This exam taught me a lesson: don't eat anything except dinner before the exam. And the check is to write quickly and carefully, don't write typos, or the right one will become wrong, and count it several times. Write the answer quickly and not carelessly, because there is still time to check later. I will work harder this month, because I will face a final exam instead of a quiz. I will definitely work hard and try my best to get better results in the exam.

7. Today, the teacher asked us to verify the constant law of quotient in division with a calculator. I gave several examples, such as: Example 1: 16 ÷ 2 = 8 cases 2: 6 ÷ 2 = 3 cases 3:1200 ÷ 200 = 6160 ÷ 20. From the above example, I know that in the organization,

And when the divisor and divisor are simultaneously expanded (or reduced) by the same multiple, the quotient remains unchanged.

8。 February 14 Saturday sunny.

Today is another sunny day. I was wandering in the street when I suddenly saw a lot of people gathered not far away. I ran for a year, and the result was a prize-winning game. "Hum, what's fun about winning the prize?" I was bored when the person next to me quickly said, "It's not fun to grab the prize, but there is a big prize that can attract people." I asked eagerly, "What is it!" "50 yuan money." The man with big eyes said. I'm very excited to hear that. "I have to try anything for such an attractive prize." Then I asked the shopkeeper how to grasp the rules. The shopkeeper said, "This is 24 Mahjong, and it says 12 5, 12 10. You can only catch 12 mahjong at a time. If the total number of 12 mahjong targets is 60, then you can win the 50 yuan Prize. " Without rolling up my sleeves, I took out 5 yuan money from my pocket and gave it to the shopkeeper.

Although I won 10 times, I still didn't win the grand prize.

When I got home, I thought about it and felt something was wrong. I think, to get 60 points, all 12 mahjong should be marked with 5. In the best case, the first 1 second catch 1 5, the second catch of two 5 s and the third catch of three 5 s will cost at least 6 yuan money. But what if the target number of mahjong is 10 or the sum of the two is the same, how many times will it cost?

Finally, after some consideration, I finally figured it out. I rushed into the street to get revenge, but I already ran away.

Saturday, February 28th will be fine.

When I read the newspaper today, I saw such a topic: Find the surface area of a cone.

[Title] A cone, the diameter of the bottom surface is 6 meters, and the length from the apex of the cone to any point on the circumference of the bottom surface is 5 meters. Find the surface area of this cone.

Although I have never learned to calculate the surface area of a cone, I have learned the surface area of a cylinder. By solving the surface area of cylinder, I know that the surface area of cylinder is equal to one side plus two bottom areas, while the surface area of cone is one lateral area plus one bottom area, and the side is a sector. Although I haven't studied it, I have checked the information and know that the area of a sector is: the area of a sector = the arc length × the radius of a circle × 1/2, which is already in the title.

That is18.84× 5×1/2 = 47.1(square meter), use the last one.

Together with the bottom area, the surface area of the cone is 47.1+3.14× (6/2 )× (6/2) = 75.36 (square meter).

Mathematics is the gymnastics of thinking. As long as we study hard and think hard, we will certainly overcome the problems and embark on the road to success!

Friday 12

Calculate wages

Dad came back from work at noon, humming a tune,

Slowly stepping into the house, I greeted him and asked, "Dad, what's so happy today?" Dad said, "I got a raise this month." I asked, "How much salary do you get now?" Dad thought for a moment, smiled and said, "My salary is higher than your mother's. 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?" "Is there any other way?" I said in surprise. 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. ...