Solution: Because after (4+2) passes, the remaining wood accounts for 25% of the total.
Therefore, there are (4+2) trips in total (1-25%).
Therefore, * * * needs (4+2) ÷ (1-25%) = 8 times.
In other words, it takes (8-4) trips to transport the "remaining 20 cubic meters of wood".
Therefore, * * has: 20 ÷ [(4+2) ÷ (1-25%)-4] × [(4+2) ÷ (1-25%) = 40 cubic meters.
2. To build a section of road, it takes 40 days for team A and 24 days for team B.. Now the two teams are working at the same time, and the result is to meet at a distance of 750 meters from the midpoint. How long is this road?
Solution: team a's efficiency 1/40, team b's efficiency 1/24.
Cooperation requirements:1÷ (1/40+1/24) =15 days.
After 15 days, Party A repairs 1/40× 15=3/8, and Party B repairs 1/24× 15=5/8.
Meeting at a distance of 750m from the midpoint means that B is 750× 2 =1500m longer than A..
B is 5/8-3/8 longer than A =1/4.
Therefore: total length: 1500 ÷ 1/4 = 6000m.
3. Two people, Party A and Party B, can complete nine eightieth of the project every day. If Party A works alone for eight days and Party B does it alone, it will take 10 days. How many days does it take for Party A and Party B to work alone?
Solution: The sum of the work efficiency of both parties is 9/80.
Let the working efficiency of A be X, then the working efficiency of B is 9/80-X..
Therefore: 8x+ 10×(9/80-x)= 1.
Therefore: x =116, 9/80-x= 1/20.
That is, it takes 16 days for Party A to do it alone, and 20 days for Party B to do it alone.
4. A project needs to be completed in 6 days, 9 days and 65,438+05 days. How many days does it take for Party A, Party B and Party C to cooperate now?
Solution: The cooperation between Party A and Party B takes 6 days to complete, so the sum of work efficiency of both parties is 1/6.
So the sum of ergonomics of B-C is 1/9, and that of A-C is115.
Therefore, the sum of the working efficiencies of A, B and C is (1/6+1/9+115) ÷ 2 = 31180.
Therefore, the tripartite cooperation between Party A, Party B and Party C needs1÷ 3180 =180/31day.