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Find a difficult problem in fifth grade mathematics
1. Party A and Party B start from the same place on the ring road at the same time and walk with their backs to each other. It is now known that it takes 70 minutes for A to walk once. If A and B meet at the 45th minute after departure, how many minutes will it take them to walk?

2. Party A and Party B can complete a project in 8 days, and Party B and Party C can complete it in 6 days; The cooperation between Party C and Party D can be completed in 12 days; Then how many days can the cooperation between Party A and Party B be completed?

3. A project will be completed by Party A alone for 20 days and Party B alone for 30 days. If Party A does it for a few days first and then Party B does it, it will take 25 days to finish it. Q: How many days do A and B work respectively?

4. To manufacture a batch of parts, Party A and Party B can cooperate for 8 days, and Party A can finish it alone in 12 days. If Party B moves ahead a few days, Party A will continue to do it, and it will take both parties 15 days to complete all the work.

5. A project can be completed within 30 days after the cooperation between Party A and Party B. 12 days later, the remaining projects will be completed by Party A alone in 24 days. Q: How many days will it take for this project to be completed by Party A and Party B alone?

6. With the cooperation of Party A and Party B, a project can be completed in 12 days; if Party A works in 10 days, Party B will continue to work in 15 days. Q: How many days will it take for Party A and Party B to complete this project alone?

7. It takes 2.4 days for Party A and Party B to complete a project, while it takes 6 days for Otsuichi to complete a project alone. If Party B starts work on the first day and Party A continues to do it on the second day, how many days will it take to complete this project?

8. A project can be completed in 0/2 days for Party A, 0/5 days for Party B and 0/8 days for Party C. Today, Party A starts work on the first day and Party B does it on the second day. On the third day, Party C will do it in Liao's order. How many days will it take to complete?

9. An express train and a local train leave from Station A and bilibili at the same time. /kloc-After 0/2 hour rendezvous, it will take 8 hours for the express train to reach bilibili, and several hours for the local train to reach Station A?

10. A job. A will be finished by B in five hours, and it will be finished in three hours. After B has done it for 9 hours, A can do it and finish it in 3 hours. So how many hours can B do after A does 1 hour?

1 1. Children's Map Give Children Cookies. If only for large classes, each person gets 15 acetylene. If you give it to children in large and small classes, it's 6 yuan each. If it is only given to children in small classes, how much will each person get?

12. There are two water pipes A and B in the water area. Open pipe A for 3 hours and 20 minutes to fill half the pond, and then open pipe B to inject water together. It takes 2 hours 15 minutes to fill the pond. If pipe B can be filled with 13 cubic meters of water every hour, what is the volume of this pool?

13. There are two groups of workers, A and B, who are both working on the same project. If No.9 is completely completed by Group A and No.27 is completely completed by Group B, how many days can this project be completed with the cooperation of Group A and Group B workers?

14. There is a project, 12 is completed by Party A alone, and 18 is completed by Party B alone. If Party A has a day off, how many days will it take to finish?

15. For a project, if Party A works alone for 2 hours, the clock for completing all the work will be completed. If three people cooperate at first, how many hours will it take to complete all the projects?

16. Party A and Party B completed a project in eight days, Party B and Party C 10 and Party A and Party C 12. How many days will it take for Party A, Party B and Party C to complete this project now?

17. When Party A and Party B cooperate on a project, it takes 15 for Party A to stop working for five days, and it can be completed in 12 days if Party A does not stop working. Q: How many days does it take to do this project independently?

18. A job, completed alone, takes 12 days to complete. B takes 15 days to complete, and C takes 20 days to complete. Now Party A and Party B will cooperate for 4 days, and then Party C will participate. Q: How many days does it take C to participate in the project?

19. If a job is completed alone, Party A needs 10 days, Party B needs 15 days, and Party C needs 20 days. Now Party A, Party B and Party C are cooperating, but Party A has to leave halfway and it will take 6 days to complete it. Q: A left after working for a few days?

20. A class of students planted trees, 100 Chinese fir seedlings and poplar seedlings. Each group was divided into 6 Chinese fir seedlings and 8 poplar seedlings. In this way, the Chinese fir seedlings have just been beaten, and there are two poplar seedlings left. How many Chinese fir seedlings and poplar seedlings are there?

2 1. With 8 kilograms of silk, you can weave silk with a width of 6 centimeters with 4 meters. Now silk has 10kg. How many meters can a 7.5 decimeter wide silk weave?