Question

Mary can clean an office complex in 5 hours. Working together John and Mary can clean the office complex in 3.5 hours. How long would it take John to clean the office complex by himself?

Answer 1

Answer:

4 hours

Step-by-step explanation:

Let x = time it would take for John to clean office alone

then

3.5(1/5 + 1/x) = 1

Multiplying both sides by 5x:

3.5(x + 5) = 5x

3.5x + 17.5 = 5x

17.5 = 1.5x

17.5/1.5 x

175/15 = x

35/3 = x

11 2/3 hours = x

or

11 hours and 40 minutes = x

.

6. Working alone,Maria can complete a task in 100 minutes.Nora can complete the same task in two hours.They work together for thirty minutes when Cita,the new employee,joins and begin helping.They finished the task 20 minutes later.How long would it take Cita to complete the task alone?

 

.

First, convert the 2 hours into minutes:

2*60 = 120 minutes

.

Let x = time it takes Cita to complete task alone

then

30(1/100 + 1/120) + 20(1/100 + 1/120 + 1/x) = 1

Multiplying both sides by (100)(120)x:

30(120x + 100x) + 20(120x + 100x + 12000) = 12000x

Divide both sides by 10:

3(120x + 100x) + 2(120x + 100x + 12000) = 1200x

360x + 300x + 240x + 200x + 24000 = 1200x

1100x + 24000 = 1200x

24000 = 100x

240 minutes = x

or

4 hours = x

So Cita can do the task alone in 4 hours.

Answer 2

Answer:

Mary can clean an office complex in 5 hours.Working together John and Mary can clean the office complex in 3.5 hours.How long would it take John to clean the office complex by himself?

6. Working alone,Maria can complete a task in 100 minutes.Nora can complete the same task in two hours.They work together for thirty minutes when Cita,the new employee,joins and begin helping.They finished the task 20 minutes later.How long would it take Cita to complete the task alone?

thank u very very much!