1. The second grade of primary school practices Olympic Mathematics every day.
1, Find the circumference skillfully. In the second year, find the circumference skillfully. Olympiad contest: Ming Ming used a 30-decimeter-long black line to set a black border for his photo. The width of this rectangular photo frame is 6 centimetres. Do you know how long this photo frame is?
Answer: 30÷2-6=9 (decimeter)
To sum up, the length of this black line is the circumference of this rectangle. Let the students understand by reading the known conditions. The perimeter and width of this problem are known. What is the length of a rectangle? There are two solutions:
Method 1: Subtract two widths from the perimeter, that is, two lengths, and then divide by two, that is, a long length. Formula: (30-6×2)÷2=9 (decimeter)
Method 2: Divide the perimeter by 2, that is, the length plus the width, and then subtract the width, that is, the length of the rectangle. Formula: 30÷2-6=9 (decimeter) By comparison, the second method is simpler.
Step 2 Find the circumference skillfully
After two squares of the same size are put together into a rectangle, the circumference is 4 cm less than the sum of the original two squares. What is the circumference of the original square?
Answer: 2×4=8 cm.
Just spell out the abstract. When two squares make up a rectangle, the eight sides that make up two squares subtract two sides, and the sum of these two sides is 4 cm, then the length of one side is 4÷2=2 (cm). The circumference of a square is 2×4=8 cm.
2. Practice Olympiad every day in the second grade of primary school.
1. The store returned 28 TV sets. I sold some, and there are still 15 sets left. How many sets have you sold? 2. Calculation: 23+20+19+22+18+21.
3. The page number range of a book is 1 to 62, that is to say, * * * has 62 pages. When adding up the page numbers of this book, another page number was added by mistake. As a result, the total is 2000.
Q: What is the page number added again?
4. Weight of a barrel of oil 10 kg. After pouring out half, the barrel weighs 5.5 kilograms. How many kilograms of oil are there?
5. Party A and Party B walk in opposite directions in two places at the same time, and meet at E. Party A continues to walk at B, and Party B takes a rest 14 minutes, and then continues to walk at A. When Party A and Party B arrive at B and A respectively, they turn back immediately and still meet at E. Know that A walks 60 meters per minute, B walks 80 meters per minute, and how many meters are there between A and B.
3. Practicing Olympiad Mathematics every day in the second grade of primary school.
1. After Kobayashi ate eight cookies, Kobayashi now has four cookies. How many biscuits did Xiao Lin eat? After my brother gave my brother five pencils, there were six left. How many pencils does my brother have?
There are 8 boys in the Second Squadron, and there are as many girls as boys. How many students are there in the second squadron?
4. Dahua and Xiaogang each have 10 pictures. After Dahua gave Xiaogang two, how many more did Xiaogang have than Dahua?
Mother cat gave Xiaobai 5 fish and Xiaohua 4 fish. Xiao Bai and Xiao Hua ate six fish. How many people are there?
6. The students borrowed balls from the gym, nine from Class One and six from Class Two. How many balls were lost in the gym?
7. After taking out five white balls and five flower balls from the cloth bag, there are 10 white balls and five flower balls left. How many white balls and flowers are there in the bag?
8. Fangfang made 14 flowers, Jingjing made 8 flowers, and Fangfang gave Jingjing several flowers. So they both have as many flowers?
9. Mom bought some duck eggs and 12 eggs. I ate eight eggs, and there were as many eggs left as duck eggs. How many eggs did mom buy?
10, there are 10 sheep on the grass, three white goats have escaped and seven black goats have come. How many sheep are there now?
4. Practicing Olympiad Mathematics every day in the second grade of primary school.
1. Boiling water to make tea takes 1 minute, boiling water takes 1 minute, washing teapot takes 2 minutes, washing teacups takes 2 minutes, and taking tea takes1minute. How to arrange tea as soon as possible? 2. There are 137 tons of goods transported from place A to place B. The load capacity of large trucks is 5 tons, and that of small trucks is 2 tons. The fuel consumption of large trucks and small trucks per train is 65,438+00 liters and 5 liters respectively. How to choose vehicles to minimize fuel consumption in transportation? How many liters of oil does * * * need to consume at this time?
3. Bake the cake in a pan. Only two cakes can be put on the pan. Bake the cake for 2 minutes on one side and 4 minutes on both sides. It takes at least a few minutes to bake three cakes now.
4. Party A, Party B, Party C and Party D go to a small tap to use water at the same time. It takes 3 minutes for Party A to wash the mop, 2 minutes for Party B to wash the rag, 1 minute for Party C to receive water in a bucket, and1minute for Party D to wash clothes. How to arrange the order of water use for four people to make them spend the least total time, and find out this total time.
5. It takes four people to cross the bridge 1 minute, 2 minutes, 5 minutes, 10 minutes. Because it is dark, they have to use flashlights to cross the bridge, but they always have only one flashlight, and the bearing capacity of the bridge is limited, which can only bear the weight of two people at most, that is to say, two people can pass at most at a time. Now I hope I can cross the bridge in the shortest time. How can I finish it in the shortest time? You can arrange it for them. What's the shortest time?
5. Practice Olympiad every day in the second grade of primary school.
1. After my brother gave my brother two pencils, there were five left. At this time, both of them had the same number of copper pens, and my brother had a pencil (). 2. Three children, Lin Lin, Hong Hong and Fang Fang, buy candy. Linlin bought 7 capsules, Honghong bought 8 capsules, but Fangfang didn't. The three children want to share equally. Fangfang paid/kloc-0 yuan, including Lingling () and Honghong ().
3. Three people eat three steamed buns and eat them in 3 minutes; According to this calculation, it takes nine people () minutes to eat nine steamed buns.
There is a long-distance race on the circular runway. Seven people run in front of each athlete and seven people run behind each athlete. There are () athletes on the runway?
5. Put 16 chickens into five cages respectively, so that the number of chickens in each cage is different. How to put it? Please fill in the number of chickens in each cage in the five boxes below.
6. Today, Honghong is 8 years old and her sister 13 years old. 10 years later, her sister is () years older than Honghong.
7. The bus runs every 15 minutes. My brother wants to take the 9 o'clock train at 10, but it's already 9: 20 at the station, so he has to wait () minutes before taking the next train.
8. It took 24 seconds to walk from the ground floor to the third floor. Then it takes () seconds to walk from 1 building to the 6th floor.
9. The children in Class Two (1) form a rectangular team to participate in the gymnastics performance. Red left sixth, right second, front fourth, back third. There are () children in Class Two (1).
10, the parking lot starts at 8: 00 every morning, and a car is sent every 8 minutes. So from 8: 00 to 8: 40, * * * sent () cars?