1.A and b water pipes need 20 hours and 16 hours to open and fill a pool of water respectively. It takes 10 hour for water pipe c to be opened alone. If there is no water in the pool, open water pipes A and B at the same time. After 5 hours, open the drain pipe C again. How many hours does it take to fill the swimming pool?

Solution:

1/20+116 = 9/80 indicates the working efficiency of both parties.

9/80× 5 = 45/80 indicates the water quantity after 5 hours.

1-45/80 = 35/80 indicates the required water intake.

35/80 ÷ (9/80-110) = 35 means it takes 35 hours to fill it.

A: It will take 35 hours to fill the pool after 5 hours.

2. It takes 20 days for Team A to build a canal, and 30 days for Team B to build it alone. If two teams cooperate, the work efficiency will be reduced because of the influence of each other's construction. The working efficiency of team A is four fifths of the original, while that of team B is only nine tenths of the original. Now it is planned to complete the canal in 16 days, and it is required that the two teams cooperate for as few days as possible. So how many days will the two teams cooperate?

Solution: From the meaning of the question, the work efficiency of Party A is 1/20, that of Party B is 1/30, and that of both parties is1/20 * 4/5+1/30 * 9//kloc-0. A's work efficiency >: B's ergonomics.

Because it is required that "the fewer days the two teams work together, the better", Party A should be made to work faster./kloc-If it is too late within 0/6 days, Party A should cooperate with Party B.. Only in this way can the two teams work together as little as possible.

Let the cooperation time be x days, then Party A will do it alone for (16-x) days.

1/20 *( 16-x)+7/ 100 * x = 1

x= 10

A: The shortest cooperation period between Party A and Party B is 10 day.

It takes 4 hours for Party A and Party B to do a job, and 5 hours for Party B and Party C to do a job. Now, please ask Party A and Party C to work together for 2 hours, and the remaining Party B needs to work for 6 hours. How many hours does it take to finish the work alone?

Solution:

According to the meaning of the question, 1/4 means Party A 1 hour, and Party B +0/5 means Party C 1 hour.

(1/4+1/5) × 2 = 9/10 means that Party A worked for 2 hours, Party B worked for 4 hours and Party C worked for 2 hours.

According to "After Party A and Party C work together for 2 hours, Party B needs to work for 6 hours", we can know that the workload of Party A working for 2 hours, Party B working for 6 hours and Party C working for 2 hours is 1.

So1-9/10 =110 means that B works for 6-4 = 2 hours.

110 ÷ 2 =1/20 indicates the work efficiency of Party B. ..

1 ÷ 1/20 = 20 hours means that it takes 20 hours for Party B to complete it alone.

A:B It takes 20 hours to finish it alone.