Math Weekly Volume II of Grade Four1It will be fine on Wednesday, May 20th.
One day, a teacher wanted to test his students' mathematics. So, he said in a math class, "I will give each of you a piece of paper and write any four numbers on it." I dare say that the difference between the two numbers written by everyone can be evenly divided by three! " "The students didn't believe it, so the teacher sent a piece of paper. After a while, everyone wrote.
When the students read and write the good numbers one by one, the teacher can find two numbers divisible by 3 on a business trip. No one is an exception! For example: 20xx, 1765, 1736, 1376 ... The difference between these two numbers can be divisible by 3. What's going on here? It is found that when any natural number is divided by 3, there are only three possibilities for the remainder, namely, the remainder 0, 1 and 2. If natural numbers are classified according to the remainder after division by 3, they can only be divided into three categories.
And the teacher asked the students to write four numbers, so there must be two numbers with the same remainder. Subtract two numbers with the same remainder (reduce the large number), and the difference can of course be divisible by 3! After the students understood, they cast an admiring look at the teacher. Students, don't you want to have a try?
Mathematics Weekly, Grade 4, Volume 2 Wednesday, May 20th will be sunny.
One day, a teacher wanted to test his students' mathematics. So, he said in a math class, "I will give each of you a piece of paper and write any four numbers on it." I dare say that the difference between the two numbers written by everyone can be evenly divided by three! " "The students didn't believe it, so the teacher sent a piece of paper. After a while, everyone wrote.
When the students read and write the good numbers one by one, the teacher can find two numbers divisible by 3 on a business trip. No one is an exception! For example: 20xx, 1765, 1736, 1376 ... The difference between these two numbers can be divisible by 3. What's going on here? It is found that when any natural number is divided by 3, there are only three possibilities for the remainder, namely, the remainder 0, 1 and 2. If natural numbers are classified according to the remainder after division by 3, they can only be divided into three categories.
And the teacher asked the students to write four numbers, so there must be two numbers with the same remainder. If two numbers with the same remainder are subtracted (the larger number is subtracted), the difference can of course be divisible by 3! After the students understood, they cast an admiring look at the teacher. Students, don't you want to have a try?
Do you know how to solve the formula: 9 1+92+93+94+95+96+97? Maybe you think there are only one or two, so let me tell you that there are three solutions to this problem.
First, these numbers can be directly calculated by the sum formula of arithmetic sequence with an error of 1.
(9 1+97)*7/2= 188*7/2=658
Second, because these numbers are close to 100, we regard these seven numbers as the sum of 100, so we add 9+8+7+6+5+4+3, and finally subtract the sum of these numbers from 700.
9 1+92+93+94+95+96+97= 100*7-(9+8+7+6+5+4+3)=700-42=658
The third type: among these seven consecutive natural numbers, 94 is in the middle, the first number 9 1 is 6 less than the last number 97, and then 6 is divided equally to 9 1, so 9 1 and 97 become two 94. Similarly, 92 and 96, 93 and 95 can all become 94, so seven numbers become seven 94.
9 1+92+93+94+95+96+97=94*7=658
Mathematics Weekly, Grade Four, Volume II, Sunday, April 26th, sunny
Today, my mother said to me, "Xue Fei, play a game with you!" " "I said," good! "
Mother brought a round cardboard and fixed a pointer in the center of the cardboard with a nail. The cardboard is divided into 24 squares on average, in which 1-24 is written respectively. "Mom, what are the rules of the game?" "The rules of the game are simple: when the pointer points to an odd or even cell, the next number must be added. Adding up to a singular number means I win, and adding up to a double number means you win. "
I played more than a dozen times in a row and lost every time. "Why is it always singular?" I asked my mother. Mom said, "Think for yourself!" So, I racked my brains and finally reminded me: odd+even = odd. Now I understand that if the pointer turns to the singular case, then adding the next number is an even number; If the pointer points to an even grid, the next number added is singular. Therefore, when the pointer points to any grid, the total number is singular.
Mathematics Weekly Diary, Grade Four, Volume II, 5 X month x day x week x day x day x
I am a "math idiot", but at the same time I am also a little math fan. In our daily life, we encounter math problems every day. I met a math problem again today.
This morning, my family ate the cake baked by my mother. I want to eat two cakes, my father wants to eat three cakes, my mother wants to eat two cakes, and my sister only needs 1. At this time, my mother asked me how to eat cake as soon as possible. How many minutes will it take? I immediately thought of baking one by one, but it takes about 3 minutes to bake one side of a cake. When can I have the cake I want? I thought again, my mother bought a pot so big that she only burned one cake at a time. It's a waste of space in the pot. You'd better bake more cakes at a time. "Mom, how many cakes can a pan bake at most?" Mom replied, "You can only bake two cakes at most". When I heard my mother say this, I began to calculate with confidence. It takes 3 minutes for two cakes to bake one side at a time and 6 minutes for two sides. A total of eight cakes are needed, and eight cakes can be divided into four and two cakes, so it takes six minutes to bake two cakes at the same time, which is equal to 24 minutes. All the formulas are: 2 × 3 = 6 (minutes), 8 ÷ 2 = 4 (pieces), 4 × 6 = 24 (minutes). I told my mother what I thought, and my father heard it and said to my mother, "Yes, that's great!" " ! I also smiled happily.
Mathematics is everywhere in life, which makes me deeply like mathematics. It exudes charming charm and fascinates me.
Mathematics Weekly, Grade Four, Volume Two, Sunday, June 26th, sunny.
On Sunday, my father and I went shopping.
When we came to the place where tomatoes were sold, my father asked, "How much is it?" The boss said, "1 yuan 2 jiao 1 kg." "I'll buy 3 Jin." Dad said. The boss weighs 3 Jin. Dad asked me, "Do the math, how much is a * * *?" I think: easy, 1. Isn't 2 times 3 equal to 3? 6 yuan! I readily replied: "3. Six dollars. " Dad's humor
Whispered: "Congratulations, you got it right!" "After dad paid the money, he went to the place where he sold vegetables. He asked, "How much is this cabbage? 1 kg? " The female boss said, "1 50 yuan." Dad asked me again, "I bought 2 Jin." Now I have 5 yuan money. How much should the boss refund me? "I think: 1. Five times two equals 3 yuan, and 5 yuan minus 3 yuan equals 2 yuan. " I replied, "change 2 yuan." Dad said, "Yes!"
Walking out of the market, I suddenly realized that mathematics is often used in my life.
Mathematics Weekly, Grade Four, Volume 2, 7, May 20th, Wednesday, sunny.
I am a "math idiot", but at the same time I am also a little math fan. In our daily life, we encounter math problems every day. I met a math problem again today.
This morning, my family ate the cake baked by my mother. I want to eat two cakes, my father wants to eat three cakes, my mother wants to eat two cakes, and my sister only needs 1. At this time, my mother asked me how to eat cake as soon as possible. How many minutes will it take? I immediately thought of baking one by one, but it takes about 3 minutes to bake one side of a cake. When can I have the cake I want? I thought again, my mother bought a pot so big that she only burned one cake at a time. It's a waste of space in the pot. You'd better bake more cakes at a time. "Mom, how many cakes can a pan bake at most?" Mom replied, "You can only bake two cakes at most". When I heard my mother say this, I began to calculate with confidence. It takes 3 minutes for two cakes to bake one side at a time and 6 minutes for two sides. A total of eight cakes are needed, and eight cakes can be divided into four and two cakes, so it takes six minutes to bake two cakes at the same time, which is equal to 24 minutes. All the formulas are: 2 × 3 = 6 (minutes), 8 ÷ 2 = 4 (pieces), 4 × 6 = 24 (minutes). I told my mother what I thought, and my father heard it and said to my mother, "Yes, that's great!" " ! I also smiled happily.
Mathematics is everywhere in life, which makes me deeply like mathematics. It exudes charming charm and fascinates me.
Mathematics Weekly, Grade Four, Volume 2, Sunday, September 26th, sunny.
Today, my father and I went to the bookstore to buy books.
We came to the bookstore. I picked out a long-awaited book and went to the cashier. Dad said, "Your book is 12. 6 yuan,
My book is 16. Three dollars, and I'll take three more 1. 5 yuan gave 50 yuan a ballpoint pen. How much is left? If you guess correctly, the remaining money can buy you ice cream. I think: 50 minus 12. 6 plus 16. 3 plus
1。 The sum of 5 times 3 is equal to 16. 6 yuan. I said, "16. Six dollars. " "Well, this 16. I will buy you ice cream for 6 yuan. " Dad said happily
When I came to the ice cream shop, my father asked me again, "I'll buy two 1." I spent 16 yuan to buy this ice cream. 6 yuan, how much money is left? "I think: simple, 16. 6 minus 1. 5 times 2 equals 13. 6 yuan. I said, "There are 13 left. 6 yuan. " Dad said, "Not bad! Not bad. " I said angrily, "You underestimate me. This is a topic for two years. If I don't know all this, am I still a fourth grader? "
Mathematics is inseparable from life.
Mathematics Weekly, Grade 4, Volume 2 9 Wednesday, May 20th will be sunny.
The number χ is very special. It looks like an "X".
One day, several digital friends such as "1", "2", "3" and "4" got together to compare the sizes.
Suddenly "χ" appeared in front of them and said, "Stop competing! You are no match for me! " 1 said, "How can you compare with us? You don't even know what you are, and you dare to come here and compete with us. Hey, what a young man! "
Not convinced, χ jumped in front of χ 1 and said loudly, χ- 1 = 9, χ=9+ 1, χ= 10. Look, I am older than 9! "
As soon as it heard "0" in the cave, it rolled out, pulled the number "1" and ran to "χ" and said, "χ× 1=0, χ=0, which is smaller than anyone else."
After hearing "0", "χ" is no longer proud.
Math Weekly Volume II, Grade 410 It was sunny on Sunday, September 26th.
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.