Math diary 1 in Grade 6 is inseparable from mathematics!
I did something at home today, that is, I measured a one-dollar coin.
The tools are: a set of rulers, a one-dollar coin and a colored pen.
First, use crayon to draw the diameter of a one-dollar coin, 2.5 cm. Calculate the circumference of a circle, and multiply 2.5 by 3. 14 equals 7.85 cm. If you understand the radius of a circle, you should multiply 3. 14 by 2 to find the circumference of the circle.
I also understand that the line segment connecting the center of the circle and any point on the circle is called diameter, which is generally represented by the letter R. The line segment passing through the center of the circle with both ends at the center is called radius, which is generally represented by the letter D. The center of the circle determines the position of the circle, and the radius determines the size of the circle.
I had nothing to do at home today, so I found an old four-wheel drive wheel. I began to measure its circumference. It's hard to find points, so I borrowed several methods from a class. It is difficult to measure because the wheels are installed there. Finally, I drew a circle on the paper according to the size of the wheel.
Measure the diameter. 3.14× 2,5 = 7.85 (cm).
This is really an interesting measurement!
Before Grade Six, math diary II, I always thought that "countdown" meant to reverse this number. For example, the reciprocal of "6" is "9". Later, I learned that the reciprocal is "the product of two numbers is 1, so these two numbers are reciprocal".
If you want to find the reciprocal of 3, you can use this method, 1÷3= 1/3, so the reciprocal of 3 is 1/3.
Then, I have a question. What is the reciprocal of "0.4"? Is it "4"? Then I tried to find the reciprocal of 4. According to the above method, the reciprocal of 4 should be 1/4, which is 0.25. Oh, it suddenly occurred to me that we should put 0. Four components are 2/5, so there is 1÷2/5=5/2, and the reciprocal of 0.4 is 5/2.
In this way, I feel strange again. What is the reciprocal of "1"? What about the reciprocal of "0"? I tried to find 1÷ 1= 1 with the help of the concept of reciprocal, so the reciprocal of 1 is itself. But 0 is not divisible, so the reciprocal of 0 is 0. Oh, there is no reciprocal of 0.
It turns out that learning "countdown" is not by rote memorization. As long as you "play" with your heart, you can turn to the small universe of mathematics and produce sparks of wisdom.
Math diary 3, a sixth-grade student, became interested in the club on a whim today. There are four problems that bother me. How big is the community? How many families are there in a building? How many households are there altogether? How much is included besides the building?
In order to solve the problem, I made a survey and found that the residential area is 200 meters long from north to south and 80 meters wide from east to west, and 200*80= 16000 (meters), so I solved the residential area, which is about 16000 square meters. The second question is the number of households in each building. Take Building 6 where my family lives, for example. The building is 25 stories high, with two units and two households in one unit. The number of households is 25*2*2= 100 (households). There are 100 households in Building 7 and Building 6, and 17 floors in Building 4 and Building 5. Each building should have 17*2*2=64 households. Buildings 1, 2 and 3 are the shortest buildings in the community, and each building has only 1 1*2*2=44 households. The third question just adds up the figures just calculated; 100+100+64+64+44+44 = 460 (households). As the saying goes, although sparrows are small and complete, there are many greening, parking lots, fitness equipment and roads in our community. The greening of the community is as high as 30%, the average building spacing is 40 meters, there are 20 ginkgo trees and 0/5 phoenix trees-there is also a fish pond in the middle of the community, which can relax people. Speaking of which, back to the topic, I calculated that each building covers an average area of 570 meters, and seven buildings add up to 570*7=3990 (square meters). The area excluding buildings should be16000-3990 =12010 (square meters).
Mathematics is really wonderful, and there is still a lot of knowledge waiting for us to explore and discover.
Math diary, Grade 6 and Grade 4, met several questions I didn't know when she was doing her summer homework today.
The first line is: the numerator of a number is 72 smaller than the denominator, and it is 5/ 13 after division. What is the score?
The second question is: the sum of the numerator and denominator of a fraction is 53. If 17 is added to the denominator, the score can be reduced to one sixth. What is the score?
I took my exercise book and asked my father how to calculate it. Dad said, "Look, the numerator of the first question is small 8, the denominator after the divisor, and the numerator before the divisor is 72 smaller than the denominator. When you can find the divisor, the numerator and denominator are reduced by 9 times at the same time. If you divide in turn, it is 13 times 5 times 9 times 9, and finally it is equal to 45 times 17. 45/ 1 17 is the answer to this question. Very simple. " "Well, it's simple! Then I will do the second question. " I said. "You see this problem is like this: the sum of the numerator and denominator of a fraction is 53. If 17 is added to the denominator, the score can be reduced to one sixth. What is the score? Well, it turned out to be ten out of forty-three. Because the sum of the numerator and denominator of the original number is 53, if the denominator is added with 17, the sum of the numerator and denominator of the new score is 70. If this condition is met, only 10 of the 60 scores can be converted into one sixth, and the denominator is 10 after subtracting 17 from 43. So the answer is ten out of forty-three. "
I learned a new method to solve problems today.
On the fifth Sunday in grade six in math diary, Yang Wen and I played 2 1 point. The rules of the game are simple: everyone draws four cards respectively, and then uses these calculation methods of "+,-,×, ⊙", and the final number must be 24.
The game started, and we each drew four cards. Alas! How bad my cards are! Listen, four people are all trump cards. At this moment, I only heard Yang Wen say, "I can do it. You see, 5+5= 10, 10×2=20, 20+4=24. " I lost the first round. But I am not discouraged, because there are still opportunities in the future, and I must seize them and strive for them. I drew four more cards "6, 5, 8, 3". I was so excited that I blurted out immediately: "6-5= 1, 8× 3 = 24,24 ÷1= 24. At this moment, 1 is equal to 1. "
Yang Wen said, "Anyway, I must beat you in the next round." The third round arrived, and I drew four more cards "10, 9, 6, 10". I was dumbfounded at first sight. Suddenly, Yang Wen shouted: "6× 4 = 24,24+1-1= 24. 2 1 I won. " I watched him smug and helpless.
Although I lost the game, I think blackjack is really interesting and math is really wonderful. I will study math well in the future and use the mixed operation of "+,-,x, ⊙" flexibly. In the next 2 1 point game, I must skillfully use it and become a master.
Today, my mother said to me, "I am free these two days." Let's go to Beijing. " So we set off. When I arrived in Beijing, there were people everywhere. Some people are performing dragon dances to celebrate the Olympic Games.
Some people are still selling some Fuwa trinkets. We went anywhere we were busy, but we forgot to find a hotel. It was dark in the blink of an eye, and my mother suddenly remembered to find a hotel. She said to me, "Founder, you are just watching the fun, and you haven't found a hotel yet!" " "
I said, "Oh, I forgot, too. Go! " But we searched for a long time and couldn't find a suitable hotel. Walking past a shop, we approached the waiter and asked him, "Is there a hotel near here with few people?" The waiter said, "Oh, you are looking for a hotel. There is a Peace Hotel along Jianshe Street. Very few people. Where have I just passed? However, there are many hotels in Jianshe Street, so don't get the wrong one. " "Do you know the house number of that hotel?"
I said anxiously. "I only understand that the house number of the Peace Hotel is double digits, and the sum of the two numbers is 6. The product of these two numbers is 9 times the quotient obtained by dividing these two numbers. " I thought about it and said to my aunt, "thank you!" " I dragged my mother to the Peace Hotel. Do you understand how I worked it out? First of all, I think the numbers whose sum of two numbers is 6 are these: 1 and 5, 2 and 4, 3 and 3, 6 and 0. First of all, 1 and 5,1× 5 = 5,5 ÷1= 5, so this does not meet the conditions. Look at 2 and 4, 2×4=8, 4÷2=2, which does not meet the conditions. Then look at 3 and 3, 3×3=9, 3÷3= 1, and the fitting conditions. In the end, 6 and 0, 0×6=0, 6÷0 does not hold water and does not meet the conditions. The answers are only 3 and 3. Sure, the house number is 33. We quickly found the Peace Hotel and spent a sweet night there.