When I arrived at the shopping mall, I saw two kinds of noodles for me to choose from, one was 450g, and the other was 400g, which was 2/3 of the price of the first kind of noodles, 4.5÷3= 1.5 (yuan), 1.5×2=3 (yuan), and I ate it alone at home. It suddenly occurred to me that my mother asked me to buy five shuttlecocks at two yuan each, 5×2= 10 (yuan), 10+3= 13 (yuan) and 30- 13 = 17 (yuan).
Return home,10; In 20 minutes, I prepared two eggs first, and then I watched TV.
Time flies to 12: 00, so I quickly beat eggs. After 20 minutes, a bowl of steaming noodles is ready. I wolfed down my noodles and then went to bed for a nap.
I took a nap and woke up at four. My parents will be back in two hours. I’m not doing anything right now. Suddenly I saw a pile of unwashed clothes. I immediately rushed over and started washing clothes.
It takes me five minutes to wash a dress, and one * * * gets eight clothes. I divided eight clothes into two piles, 8÷2=4 (pieces), and each pile contained four clothes. It takes me 8 * * * 5 = 40 minutes to finish washing clothes, so I have no choice but to bite the bullet and wash it.
It's 5 o'clock after washing clothes, 40 minutes after washing clothes, and more than ten minutes after waking up. My parents came back early, saw what I did and praised my ability!
The experience of "being a child's master" is very interesting. It not only enhances my self-reliance ability, but also teaches me how to manage my parents' finances better with math knowledge!
Math diary I
Month, day and week
At noon today, I was doing my math summer homework. Writing, unfortunately, I have a problem. I thought about it for a long time, but I couldn't figure out a way. The question is this:
There is a cuboid, the product of the front and the upper two areas is 209 square centimeters, and the 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 was scratching my head, a colleague of my mother came. 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.
Finally I got the result, which is 374 cubic centimeters. My formula is: 209 =119 = 2+171× 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.
Math diary 2
Month, day and week
I saw a puzzling math problem tonight. The topic is: 37 students want to cross the river. There is an empty boat at the ferry that can only take five people. How many times must they cross the river with this boat at least?
Careless people often ignore the "empty boat", that is, forget to have a gondola, so they can only take four people at a time. In this way, 37 people subtract one rowing classmate, leaving 36 students, 36 divided by 4 equals 9, and the classmate who worked as a boatman on the other side for the last time also landed 4, so it takes at least 9 trips.
Math diary III
Month, day and week
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 IV
Month, day and week
I met another math problem today, and it took me a lot of effort to solve it. The topic is: there are 30 birds in two trees, and 4 birds fly away from the second tree first. At this time, tree A flew to tree B with three birds, and the birds on the two trees were just equal. How many birds are there in each tree?
As soon as I saw the topic, I knew it was a reduction problem, so I solved it by the method of reduction problem. But when I checked, I found something was wrong. I will do it again more seriously. I think there are as many as four missing, half of them are 13, and the restored B-tree is14; A tree is 16. The formula is: (30-4) ÷ 2 = 13 (only); 13-3+4 =14 (only); 30- 14 = 16 (only). The answers are: a tree 16 and b tree 14.
By solving this problem, I understand that no matter what I do, I should be careful, otherwise, even if I master the solution to the problem, the result will be wrong.
(2)
Today, my mother gave me 10 yuan to go shopping in the supermarket. I bought a string of firecrackers 2/ 10, four lollipops/10, seven balloons 2/ 10, and finally a comb 4/ 10, a *. There is still one yuan left, and I have to pay it back to my mother.
When I got home, my mother ate 1/4 lollipops, my father ate 1/4 lollipops, I ate 1/4 lollipops, and I gave the other one to my brother Xiao Qiang next door. (Author: Xiao Enling)
(3)
Last week, we studied fractions. Fractions have numerator, denominator and fractional line, for example, 1/3, where 3 is denominator, 1 is numerator and the middle horizontal line is fractional line.
Scores are used in many places in life. For example, a book has thirty pages, and each page is 1/30 of a book. Fractions can also be used to add and subtract! For example, half plus half equals two, which is 1. Why is this happening? If you divide a cake into two parts, each part is 1/2 of the cake, and then put the two parts together, there are two parts 1/2, which is just a cake. When adding and subtracting fractions, if the denominator is the same, only the numerator is added, regardless of the denominator. And 2/2 of the numerator and denominator are the same, which is 1.
I also learned to compare the size of fractions. The teacher taught us the formula: numerator is the same as denominator, the fraction with large denominator is small, and the fraction with small denominator is large; Denominators are the same as numerators, with large numerator scores larger and small numerator scores smaller.
The teacher also reminded us that when writing scores, we usually write the fractional line first, indicating the average score, then the denominator and finally the numerator.
My colorful math dream
When I was a child, I always dreamed that I could be the first to finish the homework assigned by the teacher and get the little red flower in the teacher's hand as soon as possible. My naive dream was red at that time.
When I was a freshman, I always dreamed that I could recite mathematical formulas as soon as possible, regardless of difficulties and hardships. That is my persistent and hard-working dream, and it is orange.
In my sophomore year, I always dreamed that my math teacher was beautiful, my math class was very active and my math homework was very simple. That's my dream of relaxing. It's yellow.
When I was in the third grade, I always dreamed that I could know mathematics like the back of my hand, and I could learn some mathematical rules like my big brother and big sister in the fourth and fifth grades. This is my dream of progress. It is green.
In the fourth grade, I always dreamed that my math scores would soar, and I was among the best in my class and praised by my teachers. It was my futile dream and it was blue.
When I was in the fifth grade, I always dreamed that I had some unique thinking and explored some new mathematical theories, which could be comparable to that of mathematician Hua. That is my dream, and it is blue.
When I was in the sixth grade, I always dreamed that I had a competitor in math. That is my dream that I dare to challenge. It is purple.
That beautiful, innocent, brilliant and colorful mathematical dream brought me infinite fun, and at the same time let me know that mathematics is not just a boring number, it affects everything with its colorful brilliance and its own charm!
Mathematics learning
The math problem in school is not difficult. You can do all the questions, but there are not many times to get full marks. You either didn't see the division and combination clearly, or forgot to write the name of the unit, or you made a mistake, so one or two points will always be deducted. Ask my classmates, many people are in the same boat with me-I was careless when I answered the questions, and I regretted it after I finished it. In the final analysis, the problem is-not serious!
Calculations and exams are a tough nut to crack, so the teacher has made great efforts. For example, in order for us to find the unit "1" when doing the percentage problem, the teacher racked his brains to come up with a good method: first, judge whether "1" is known or indirect, if it is known, use multiplication, if it is unknown, use division or equation, try word for word, and mark the places that are easy to make mistakes. This method has been implemented for several days, which has greatly improved the examination of questions. However, the good times did not last long. Because it was too much trouble, I delayed the time. In a few days, I began to make old mistakes again and again. No matter what the teacher told me, many students still stumbled. Because there are few mistakes in the exam after all, everyone always takes chances and always wants to finish it quickly and not to fall behind. "Slow work makes fine work", as soon as the speed is fast, mistakes will follow. In fact, there is plenty of time for the exam, so you can do it seriously. Even in normal times, grades are not very important, but at least be serious. Our teachers all circle the questions, not to mention us. Teachers often say, "Being earnest can make up for many shortcomings in us." It's really true. Maybe some students who didn't study very well gave themselves more chances to succeed because they were serious, and lost a lot of points, while those of us who are "smart-aleck" sentenced ourselves to death while doing problems.
Success belongs to those who are prepared. In order to meet success, let's start by doing math problems, and from now on, learn to be a man and be a serious person.