Math diary's first article on area.
I have a new home. This new home has four different colors and sizes of floor tiles. You don't believe it. Let me introduce them to you one by one!
In the living room and two bedrooms, there are square floor tiles, and they are beige. Its side length is 60 centimeters and its area is 3600 square centimeters.
The floor tiles in the bathroom are silver. As soon as I saw the silver floor tiles, I thought of gold and silver in my mind! This kind of floor tile is also square. The side length is 30 cm and the area is 900 square cm. What do you find when you see two kinds of floor tiles in my house?
There are two kinds of bricks in the kitchen, one on the wall and the other on the ground. Let me tell you something about the floor tiles on the wall first. The floor tiles on the wall are silver blue, rectangular, with a length of 3 1cm, a width of 19cm and an area of 589cm2. The floor tiles on the kitchen floor are square and reddish, with a side length of 3 1 cm and an area of 3 1? 3 1=96 1 cm2，
Haha, I believe there are so many floor tiles in my house. If you don't believe me, you can come to my house and have a look. I welcome it very much.
Regional math diary II
This week, we learned about area units, which are square millimeter, square centimeter, square decimeter and square meter.
In the morning, after I finished writing my composition, my father asked me? Li Ran, did you finish your homework so soon? Let me ask you some math questions. ? I said confidently:? All right! The area of a blackboard is about 400 ()? The area of the blackboard is about 400 square decimeters. The area of that playground is about 2500 () I was dumbfounded: square decimeter. ? Dad smiled and said, think again. ? I thought for a moment: a blackboard is about 400 square decimeters, and 2500 is about six times that of 400. Ah, how can the playground be as big as six blackboards? The area of the playground should be 2500 square meters. Not bad. ? Dad smiled and said,? Then how do you know? I compared it with the quick blackboard. That's a good idea. Let me ask you one more question. Is this table 45 () wide? This table is 45 centimeters wide. ?
Answer the question, dad said? I haven't mastered the area unit yet! ? I bowed my head in shame.
Regional math diary III
Today, we know the unit of area. I know that the nail surface of my thumb is about 1 square decimeter, and the size of a thumbtack is about 1 square meter. After class, I measured that my desk is about 6 square decimeters long and 4 square decimeters wide, and its area is 24 decimeters. I also know that the area of one side of my eraser is about 8 square decimeters. After school, I went back to my home with a housing area of 150 square decimeter, touched the switch and turned on the light. I found that the size of the switch at home is about 1 square centimeter, and each floor tile at home is about 36 square meters. I was hungry, so I ate a piece of bread 1 square, and then I did my homework on a square table 1 square centimeter. Open a 24-square-centimeter math book and find that the homework is very simple. I'll finish it in a minute. I turned on the TV with a 30-square-meter screen and watched cartoons for a while. After dinner, my father and I looked at the photo album together and looked at the photos, which were about 1 square meter. I can't help laughing. I also talked with my father about today's study. Father touched my head and taught me to study hard. I took my father's palm about 1 square meter, looked at the calluses on it and said affectionately, Dad, I will definitely listen to my teacher and study hard.
Math diary's fourth chapter on area.
One day, when I was in the interest class of Olympic Mathematics, I opened my book to preview what I wanted to learn. It turns out that I learned the first lecture 14 today: pairing summation! Listen to the teacher. Pairwise summation is also called Gaussian summation, because this summation method is developed by the famous mathematician Gauss? .
When I saw Example 3, I was stumped by this question. The topic is:? There is a pile of wood stacked together, one * * * is 20 layers, the first layer has 12 root, the second layer has 13 root, and each layer below has one more root than the upper layer. How many roots are there in this pile of wood? I picked up a pencil and drew a picture on the left and a picture on the right, but I didn't work out the problem. In class, the teacher gave us a formula: trapezoid area = (upper bottom+lower bottom)? Tall? 2。 What does this formula mean? Why use such a formula? I thought for a long time, but I couldn't find the answer, so I asked the teacher this question. The teacher said: You can combine the calculation method of rectangular area. ? According to the teacher's prompt, I drew a picture in my notebook, calculated it and drew the following picture.
It turns out that the sum of the upper bottom and the lower bottom of the trapezoid is the length of a rectangle, the height of the trapezoid is the width of the rectangle, and the area of the trapezoid is half of the area of the rectangle, so it is concluded that the trapezoid area = (upper bottom+lower bottom)? Tall? 2 This formula. Because this pile of wood has become a trapezoid, we can use this formula to calculate its root number, so I quickly calculated the length of the bottom (that is, how many roots are there)12+20-1= 31(roots), and then calculated the area of the trapezoid, that is, the total root number of this pile of wood, (65433. 2=430 (root). I looked at the mind navigation. Yes! I got this question right! Yeah! ? I said excitedly.
After finishing this problem, the teacher said: Students, this kind of problem is similar to finding the trapezoidal area, which you will learn in the fifth grade. ? My heart is full of joy, because I have learned a fifth-grade arithmetic problem since I was only in the third grade, and I also know the origin of trapezoidal area formula and how to apply it to daily life.