The 2022 Hunan Provincial examination line test preparation examination: multi-person cooperation does not worry about the establishment of special value solution thousands of worries
The multi-participant cooperation problem in the project is common in the line test, but the examinee often chooses to give up this kind of topic because of the time shortage or the topic material is too long (generally more than three lines), resulting in the loss of points.But this kind of problem is easy to solve once you get your head around it.So do as much as you can with this kind of problem.The method of special value can provide you with a good way to solve the problem, and you will not be confused in the follow-up problem solving process.The formula involved in engineering problems: the total amount of work = work efficiency × work time, that is, W=Pt special value method of application.2. The ratio of efficiency that appears in the question or can be obtained by using known conditions, set the efficiency as the special value, what is the ratio of efficiency, what is the special value?The above are the two cases of setting special values, and the following questions show their specific applications.For example 1, it takes 30 days for Team A to complete a project independently, and 25 days for team B to complete a project independently.After 4 days of construction by team A alone, the two teams worked together. During this period, Team A took several days to rest. Finally, the whole project took 19 days to complete.A.1 B. 2 C. 3 D.If the total amount of work (W) is set to a special value, the least common multiple of 30 and 25 is 150, the efficiency of A can be obtained as 5 and that of B as 6.As described in the title, “Team A worked alone for 4 days, and the whole project took 19 days in the end”, it can be inferred that team B worked 19-4=15 days, then the amount of work completed by Team B is 6×15=90, then the amount of work completed by Team A is 150-90=60, and the amount of work completed by Team A is 60÷5=12 days. It is known that the whole project took 19 days.A rested 19-12=7 days.Example 2: It takes 40 hours, 48 hours and 60 hours respectively to make a batch of lanterns for the Lantern Festival by hand.If the three masters work together for 4 hours and the remaining tasks are completed by B and C together, the time spent by B in the whole lantern production process is A.24 hours B.25 hours C.26 hours D.28 hours A.Chinese public analysis:There are three hours to complete the work. Set the total amount of work W to a special value, 240, the least common multiple of 40, 48, and 60, and the efficiency of the three masters can be obtained. The efficiency of A is 6, that of B is 5, and that of C is 4.The amount of work completed by “three masters working together for 4 hours” is (6+5+4)×4=60, and the remaining tasks are completed by B and C together, which also needs (240-60)÷(5+4)=20 hours, so the whole process needs 4+20=24 hours.It takes 22 days for team A, team B and Team C to complete a project. The work efficiency of team A is three times that of Team B, and the work of team B in three days is two thirds that of Team C in two days.Three teams started work at the same time. After 2 days, team C was transferred to another site. How many more days will it take for team A and Team B to finish the project?A.20 B.28 C.38 D.42CChinese public analysis:Appear in the title “two-thirds times the b team is a team work efficiency, the b team is the three days of work third team 2 days work two-thirds”, which can get the efficiency of party a and party b for 3:2, the efficiency of ethylene propylene for for, is the ratio of the efficiency for 6:4:9 armour ethylene-propylene three, you can assume that the efficiency of 6, efficiency of 4 b, c efficiency of 9,Then the total amount of work W=(6+4+9)×22=418, the amount of work completed by “three teams working at the same time for 2 days” is (6+4+9)×2=38, the remaining amount of work is 418-38=380, and 380÷(6+4)=38 days.Through the analysis of the above three topics, we must have some understanding of the problem of multi-party cooperation, you can do more related questions, practice makes perfect.