Keywords: self-test in the second grade of primary school

This article is applicable to: the second grade of primary school.

Composition source:

This composition (600 words) is about the second grade of primary school (600 words). The title is: The Adventure from Linda (3) The Test of the Old Wolf. Everyone is welcome to contribute enthusiastically.

The test of the old wolf

Smart dog and Huahua sit on the cheetah and hum a little song. It took only three days to get to the "big jungle". Panting, the cheetah said to the clever dog, "Friends, you have just arrived in the' big jungle', which is a little far from Yang Sen's castle." Huahua asked the cheetah again, "How far is it from the castle?" The cheetah scratched his head and said, "I don't know that either." I just heard that Jack, the chief of staff of King Yang Sen, said that we should start from the main entrance of the jungle. As for how much, I don't know. " The clever dog ignored it and said helplessly, "Forget it, let's start from the main entrance as the cheetah said!" " "Smart dogs and flowers bid farewell to cheetahs and disappear into the vast forest.

Huahua ran ahead excitedly all the way. Suddenly, it stopped working. Looking at it in surprise, the clever dog rushed to have a look. There were three intersections. A sign was inserted at the first intersection, which read: Wrong intersection. A sign was also inserted at the second intersection, which read: Turn right at the intersection. A sign was inserted at the third intersection, which read: 1 Wrong intersection. There is a sign hanging high above it, which says: only one pair. I feel dizzy at the sight of these flowers. Huahua asked the smart dog, "Brother, which intersection can pass?" The clever dog said without thinking, "No.65438 +0 crossing!" Huahua asked doubtfully, "Why?" The smart dog said, "We can set the crossing of telling the truth to 1 and the crossing of telling lies to 0. So there is 1, 0, 0; 0、 1、0; 0、0、 1。 If 2 is right, then 3 is right and 3 says 1 is wrong. Although it is proved that 1 is wrong, it is impossible. There is only one right. If 3 is right, then 1 crossing is wrong, and 1 crossing is wrong, then 2 is right and impossible. 1 is right, then 2 is wrong, 2 says 3 is right and 3 is wrong. So only 1 right! " Huahua marveled at the clever dog.

The clever dog and Huahua just walked to the front and saw an old wolf sitting on the road. The old wolf said, "You have passed the previous level, and the next level is even more difficult!" " "The clever dog is not afraid of danger, patting his chest and saying," Whatever! "The old wolf sneered," However, you should limit it to 10 second, or you will be eaten! " "Huahua trembled with fear. The old wolf asked a question: "Listen carefully! The famous poet Li Bai likes to visit the great rivers and mountains of the motherland. Once he went out, he put some wine in the hip flask, and every time he met the hotel, he added wine, which doubled the wine in the hip flask. Drink 1 l every time you meet flowers; After three times, I drank all the wine in the pot and asked how much wine was left in the pot. "Huahua whispered aside and compiled the topic on Li Bai." After only three seconds, the clever dog suddenly replied, "Yes, 0.875 liter!" " The old wolf opened his eyes wide and asked the clever dog, "How did you get it?" The clever dog smiled and said, "It can be analyzed in this way. It will be difficult to calculate from the front to the back according to the known conditions. It will be much easier if you push back in the opposite direction. " Said, and drew a schematic diagram on the ground:

Drink all the wine in the pot-65438+0 liters before the third flower;

—— 1÷ 2 = 0.5 (liter) Before meeting the hotel for the third time;

Before the second flowering-1+0.5 = 1.5 (liter);

—— Before the second hotel encounter 1.5÷ 2 = 0.75 (liter);

—— 1.75÷ 2 = 0.875 (liter) Before seeing the hotel for the first time.

That is, ((1+1÷ 2) ÷ 2+1) ÷ 2 = 0.875 (liter).

The old wolf clapped his hands and shouted, "Yes, yes, this time, our kingdom of Yang Sen can turn the tide!" " The clever dog said, "Can you take me to see Yang Sen now?" "Lao lang readily agreed. The clever dog was about to leave with Huahua and the old wolf when the old wolf suddenly said, "I need this clever dog's help!" ""Huahua scrambled to say, "Let me do it this time!" "The old wolf took a contemptuous look at Huahua and said," Cut, just you! "Huahua said angrily," Only me! " The old wolf sneered, "Listen carefully! My little nephew gave me a chicken and rabbit cage covered with a big cloth the day before yesterday. But my nephew said, "don't open the tarpaulin and see how many chickens and rabbits I can count." No, I counted *** 100 with 272 legs. I don't know how many chickens and rabbits there are. "After listening to this, Huahua pondered for a while and said," I learned a lot from Brother Dog. I can solve it with equations. " Say and drew a picture on the ground:

Solution: If there are X chickens in the cage, there are (100-x) rabbits.

2x+4( 100-x)=272

2x+400-4x=272

2x= 128

x=64 .

Rabbit: 100-64 = 36 (only).

Huahua smiled after writing: "What?" The old wolf had to have the cheek to say, "You can do it!" "Three little guys happily holding hands, walked to Yang Sen's palace. ...