SOLUTION: Losing my mind here...please help. Both crew A and Crew B can lay underground cable at a rate of 2 miles per day. Crew A begins and Crew B begins 6 days later. How long does Cre

Question 27429: Losing my mind here...please help.
Both crew A and Crew B can lay underground cable at a rate of 2 miles per day. Crew A begins and Crew B begins 6 days later. How long does Crew A have to work before the job is finished. The length of the project is 40 miles.
Answer by mbarugel(146) (Show Source): You can put this solution on YOUR website!
When working together, crew A and B can lay cable at a rate of 4 miles per day (2 miles each).
Now, Crew A has already been working alone (rate: 2 miles per day) for 6 days. So there are already 12 miles of cable laid. Since the total is 40 miles, there are still 28 miles to go. But now crew B starts working too, so the rate goes to 4 miles per day. Since 28 miles are left, then they must work for 28/4 = 7 days more.
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