Now Xiaoming's family has crossed a bridge. It's dark when crossing the bridge, so there must be a light. Now it takes 1 second for Xiaoming to cross the bridge, 3 seconds for Xiaoming's brother, 6 seconds for Xiaoming's father, 8 seconds for Xiaoming's mother and 12 seconds for Xiaoming's grandfather. At most two people can cross the bridge at a time. The speed of crossing the bridge depends on the slowest one. The light turns on for 30 seconds and then goes out. Ask Xiaoming how to cross the bridge.
Let you do the first two big arithmetic problems.
Four couples sit together and chat. Of the four women, Xiaoli ate three pears, Xiaoyu ate two, Xiao Fang ate four and Xiaolian ate 1. Among these four people, Guoqiang eats as many pears as his wife, Xiangyang twice, Zhong Min three times and Wen Jia four times. They ate 32 pears together. Do you know who Zhong Min's wife is? Explain why. Do not be blind.
3. Interesting mathematical problems in ancient India
Ancient India also had a splendid culture like ancient China. The following is an interesting math problem in ancient Indian manuscripts.
There is a large swarm of bees, one fifth of which falls on azaleas and one third on gardenias. The difference between the two flew to the rose, and finally a little bee flew between the fragrant jasmine and magnolia. How many bees are there?
4. Apple IQ test
There are ten baskets of apples, each basket has ten apples, *** 100 apples. The apples in each basket weigh the same, of which 9 baskets weigh 1 kg, and the apples in the other basket weigh 0.9 kg, but the appearance is exactly the same, which can't be distinguished by eyes or hands. Now I want you to find the light basket at once with an ordinary big scale. Can you do it?
5. Primary challenges of Olympic mathematics in primary schools
Number the boxes, then take out an apple from the first box, two apples from the second box, three apples from the third box, and so on. Weigh all the apples taken out together. Less than 0. 1 indicates that the apples in the first box are light, less than 0.2 indicates that the apples in the second box are light, less than 0.3 indicates that the apples in the third box are light, and so on.
6, around your strange city problem
There is a strange city. There are good people and bad people living in cities. There is a man standing guard on the left and right of the city gate. One of them is a good man, and the other is a liar. Good people always tell the truth, and liars always tell lies. When a person arrives at this door, he forgets which side is a good person. If he asks the wrong person, he will go to the place where the liar lives and be cheated. what should he do ？
7. Little things in life that you may not know.
Here are two buckets for you. The capacity is 3 liters and 5 liters respectively, and there is a lot of water. How to accurately measure 4 liters of water?
Can you catch up with the farmer's IQ?
There are 50 people in the farmer's village, and everyone has a poultry at home. One day, the farmer came back and learned a news: the poultry in the village were infected. Villagers are required to observe the situation of poultry once a day, but everyone can only observe whether 49 poultry in other people's homes are sick, but they can't see their own poultry. When it is judged that one's own poultry is sick, the sick poultry must be shot in exchange for the survival of the whole village, but everyone has only the right to shoot his own poultry. On the first day, the farmer did not shoot; The next day, there were still no gunshots. On the third day, I heard gunshots. At this time, the farmers knew that there were several sick birds in the village. Excuse me, do you know how many?
9. The dog chasing the rabbit in the civil service exam.
The dog chased the rabbit, and the rabbit was 9 meters ahead of the dog. A dog runs five steps as far as a rabbit runs nine steps. But rabbits run fast. At the same time, the dog runs 2 steps and the rabbit runs 3 steps. How many meters can a dog run to catch up with a rabbit? What are you thinking about?
10, if you are the boss, let the workers work for you for 7 days, and the reward of the workers is a gold bar. Gold bars are divided into seven consecutive sections, and you must give them a gold bar at the end of each day. Now you are only allowed to break gold bars twice. How do you pay your workers?
1 1, stumped a person's book puzzle.
The page number of a book is 1 to n. When adding the page number of this book, another page number was added by mistake. The total error is 2005. Then the page added once must be 52. Why?
12, a junior high school arithmetic problem that scares adults
In an election campaign, a candidate arranged a campaign trip in China. We might as well arrange him by plane. I went to a place due east on the first day, flew to a place due north on the second day, flew to a place due west on the third day, flew to a place due south on the fourth day, and flew to a place due east on the fifth day ... If his flight distance on the nth day is n2/2 miles, then the end of his trip from his starting point to the 40th day is _ _ _ _ _ _ _ _ miles.
13, the easiest simple question to make people feel big.
One train left Beijing for Guangzhou at a speed of 15 km/h, and another train left Guangzhou for Beijing at a speed of 20 km/h. If a bird leaves with two trains at a speed of 30 kilometers per hour, it starts from Beijing, meets another car, and then returns to fly in the opposite direction, so it flies back and forth between the two trains in turn until the two trains meet. How long did the bird fly?
14, intelligence test: where did that money go?
Three people paid 30 yuan's hotel fee, the manager took it back to 5 yuan, and the waiter hid 2 yuan from it and gave it to everyone 1 yuan. In the evening, after learning that the waiter had hidden 2 yuan's money, one of the passengers and his companions thought about it: each of the three people got back 1 yuan, which is 3×( 10- 1). Together with the waiter, 2 yuan was 29 yuan, but they gave it to 30 yuan! Do you know where 1 yuan went?
15, intelligence survey in small things in life
There is a pile of garbage, which is stipulated to be cleaned by three families. Zhang Hu can't attend because he is out, leaving 9 yuan money to do it for him. Wang Hu worked for five hours early in the morning, while Li Hu worked for four hours in the afternoon. Ask Wang Hu and Li Hu how to distribute the 9 yuan money.
16, stumped your simple problem
Nine wine bottle caps are buckled on the table, two at a time, neither more nor less. But there is no limit to the number of laps. How many times have you turned the lid on?
17, little ants test your great wisdom.
There is a thin wooden pole of 27 cm, and there is an ant at five positions of 3 cm, 7 cm, 1 1 cm, 17 cm and 23 cm. The wooden pole is too thin to pass two ants at the same time. At first, it was arbitrary for ants to turn their heads left or right. They will only move forward or turn around, not backward. When any two ants meet, they will turn around and walk in the opposite direction at the same time. Suppose ants can walk one centimeter per second. Q: What is the shortest and longest time for all ants to leave the wooden pole?
18, a simple interview question preferred by many famous enterprises.
Being good at discovering the similarities and differences and internal relations of things and discovering the development law of things are the basic qualities and conditions for doing any research work well. Please look for it. How similar are the following two figures? What is the difference?
19, the crash is the wrong one.
There are two obvious mistakes in the problem you see, but you may not see it at the moment. You need to look carefully. Don't sleep until you find it.
20. Three penguins will still trip you.
There are three penguins, front, middle and back, side by side on the same ice.
The first one said, "The two buddies behind me."
The last one said, "The two brothers in front of me."
Strangely, the middle one said, "There are no buddies before and after!" " "
Q: Why is this?