First, Party A and Party B cooperate to complete the project in 12 days. Party A will complete the project in six days, and the rest will be completed in 21 days. If Party B does all the work alone, how many days will it take to complete it

First, Party A and Party B cooperate to complete the project in 12 days. Party A will complete the project in six days, and the rest will be completed in 21 days. If Party B does all the work alone, how many days will it take to complete it

A does it alone for six days, and B does it in 21 days
B did
21-6 = 15 days
Party A has done it for 6 days, and Party B has done it for 15 days, which can be regarded as six days of cooperation between Party A and Party B, and then Party B does it alone
15-6 = 9 days
Party A and Party B cooperate in 6 days
1 / 12 × 6 = 1 / 2
B. completed in 9 days
1-1 / 2 = 1 / 2
If the work is done by Party B alone, it needs to be completed
9 △ 1 / 2 = 18 days

For a job, team a and team B cooperate and complete the cost in 12 days. Now team a will do it alone for 6 days, and the rest will be done alone for 21 days by agent B. how many days will it take if team a does it alone?

Party A alone for 6 days, and Party B alone for 21 days
In fact, Party A and Party B cooperate for 6 days, and then Party B alone: 21-6 = 15 days
So B alone 15 days to complete the total: 1-1 / 12 × 6 = 1 / 2
1 / 2 / 15 = 1 / 30
A: 1 / 12-1 / 30
=1÷1/20
=20 days

A, B two engineering teams a total of 16 days to complete a project. Two teams 9 days of cooperation, after the home left, B alone to do 21 days to complete: ask a and B how many days to work alone

Party A and Party B complete 1 / 16 every day
9 / 16 in 9 days
Suppose that Party A and Party B complete it separately: Party A x, Party B y
9 / 16 + 21 / y = 1, y = 48
1 / x + 1 / 48 = 1 / 16, x = 24
Completed alone: A for 24 days, B for 48 days

For a job, Party A and Party B work together for 18 days. It is known that the work efficiency ratio of Party A and Party B is 2:3. How many days does party a work alone?

18*5/2=45