Bell's mother is ill. In order to earn money to treat her, Bear gets up before dawn every day to go fishing in the river and sell fish in the market as soon as possible.

One day, as soon as Little Bear set up the fish stall, the fox, the black dog and the old wolf came. When the bear saw a customer coming, he hurriedly called, "Buy fish? I just caught this fish. How fresh! " The fox turned the fish over and asked, "How much is a kilogram of such fresh fish?" "The bear grinned." Cheap, four yuan a kilo. The old wolf shook his head: "I am old and my teeth are falling out." I just want to buy some fish. "The bear looked reluctant:" I sold the fish to you, and who sold the fish head and tail? The fox wagged his tail and said, "Yes, no one wants to buy the leftovers, but Uncle Wolf has bad teeth and can only eat some fish. To tell you the truth, Black Dog and I are very good to each other. If you buy fish heads and tails, won't you help Uncle Wolf and Brother Xiong? "The bear clapped his hands, but he hesitated." Good, but at what cost? "The fox rolled his eyes and replied," 2 yuan is 1 kg, fish head and fish tail are 1 yuan is 1 kg. Isn't it 4 yuan 1kg? "The bear drew a picture on the ground with a stick, and then patted his thigh:" OK, let's start! " "The four of them started work together, and in a short time, the head, tail and body of the fish were separated. Once the bear weighed, the body of the fish was 35 kilograms of 70 yuan; Fish head 15 Jin 15 yuan, fish tail 10 Jin 10 yuan. The wolf, the fox and the black dog quickly ran to the Woods with the fish, matched the head, the body and the tail, and then divided them equally.

On the way home, Bear thought: According to 4 yuan 1 kg, I should sell 60 kg of fish to 240 yuan, but now I only sell 95 yuan ... Bear can't figure it out.

Do you know what this is about?

Interesting Story of Mathematics in Grade Three (2)

Children, do you know the story of Gauss, a mathematical genius, when he was a child? When Gauss was in the second grade of primary school, once the teacher wanted to have a rest after teaching addition, so he asked the students to do some calculations. The topic is:1+2+3+4 ...+96+97+98+99+100 =? I thought the students would be quiet for a while, but I was about to find an excuse to go out, but Gauss stopped me! It turns out that Gauss has worked it out. Little friend, do you know how he did it? Gauss told everyone how he worked it out: add 1 to 100 and 100 to1; Line up in two rows and want to add, that is:1+2+3+4+………………+96+97+98+99+100+99+98+97+96+……+4+3+. 1+10 1+1* * has one hundred101,but the formula is repeated twice, so it is 65438+. Since then, the learning process of Gauss Elementary School has already surpassed other students, which laid the foundation for his future mathematics and made him a mathematical genius.

Interesting Story of Mathematics in Grade Three (3)

Have you ever heard of the problem of "chickens and rabbits in the same cage" This question is one of the famous and interesting questions in ancient China. About 1500 years ago, this interesting question was recorded in Sun Tzu's calculation. The book describes it like this: "There are chickens and rabbits in the same cage today, with 35 heads on the top and 94 feet on the bottom. The geometry of chicken and rabbit? These four sentences mean: there are several chickens and rabbits in a cage, counting from the top, there are 35 heads; It's 94 feet from the bottom. How many chickens and rabbits are there in each cage?

Can you answer this question? Do you want to know how to answer this question in Sunzi Suanjing?

The answer is this: If you cut off the feet of every chicken and rabbit in half, then every chicken will become a "one-horned chicken" and every rabbit will become a "two-legged rabbit". In this way, the total number of feet of (1) chickens and rabbits changed from 94 to 47. (2) If there is a rabbit in the cage, the total number of feet is more than the total number of heads 1. So the difference between the total number of feet 47 and the total number of heads 35 is the number of rabbits, that is, 47-35= 12 (only). Obviously, the number of chickens is 35- 12=23.

This idea is novel and strange, and its "foot-cutting method" has also amazed mathematicians at home and abroad. This way of thinking is called reduction. Reduction method means that when solving a problem, we do not directly analyze the problem first, but deform and transform the conditions or problems in the problem until it is finally classified as a solved problem.

Interesting Story of Mathematics in Grade Three (4)

Newton, a great British scientist, once wrote a math book. There is a very famous topic in the book about cattle grazing on pasture. Later, people called this kind of topic "Newton problem".

The "Newton problem" is like this: "There is a pasture where 27 cows are known to have been raised and the grass has been eaten up in 6 days; Raise 23 cows and eat all the grass in 9 days. If you have 2 1 cow, how many days can you eat all the grass on the pasture? And the grass on the pasture is growing. "

The general solution to this kind of problem is: regard the grass eaten by A Niu Yiri as 1, then there are:

(1) The forage for 27 cows for 6 days is 27×6= 162.

(This 162 includes original grass and 6-day new grass. )

(2) The pasture eaten by 23 cows in 9 days was 23×9=207.

(This 207 includes the original grass in the pasture and the grass that has grown for 9 days. )

(3) 1 day: (207-162) ÷ (9-6) =15.

(4) The grassland is 27×6- 15×6=72.

(5) Feed new grass to 15 cows every day, subtract 2 1 cow from 15 cows, and the remaining 6 cows eat grass from the original pasture:

72 ÷ (21-15) = 72 ÷ 6 =12 (days)

Therefore, it takes 12 days to feed 2 1 cow and eat all the grass on the pasture.

Please calculate it.

There is a pasture, if you raise 25 sheep, you can eat all the grass in 8 days; Raise 2 1 sheep and eat all the grass in 12 days. If you raise 15 sheep, how many days can you eat up the grass growing on the pasture?

Interesting Mathematics in Grade Three (5)

Little Euler's father decided to build a new sheepfold. He measured a rectangular piece of land with a ruler, 40 meters long and 15 meters wide. He calculated that the area is exactly 600 square meters, with an average of 6 square meters per sheep. When he was ready to start construction, he found that his materials were only enough for the fence of 100 meters, which was not enough at all. If the sheepfold is 40m long and15m wide, then its circumference is110m. Father felt embarrassed, but little Euler told his father that all he had to do was move the stake in the sheepfold a little. He shortened the original side length of 40 meters to 25 meters centered on the stake. The original side length15m is extended, and10m is increased to 25m. In this way, the original planned sheepfold has become a square with a side length of 25 meters. My father built a fence according to the sheepfold designed by little Euler. 100 meter long fence is really enough, and the area is also enough, and it is a little bigger. Father felt very happy. Later, Euler became a famous mathematician in the history of mathematics.