SOLUTION: Jeff starts driving 55 miles per hour from the same point that Lauren starts driving at 70 miles per hour. They drive in opposite directions, and Lauren has a half-hour head start.

Question 187928: Jeff starts driving 55 miles per hour from the same point that Lauren starts driving at 70 miles per hour. They drive in opposite directions, and Lauren has a half-hour head start. How long will they be able to talk on their cell phones that have a 440-mile range?
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
Jeff starts driving 55 miles per hour from the same point that Lauren starts driving at 70 miles per hour. They drive in opposite directions, and Lauren has a half-hour head start. How long will they be able to talk on their cell phones that have a 440-mile range?
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Laura will be 35 miles away when Jeff starts. (70 mph * 1/2 hour)
Going opposite directions, they separate at the sum of their speeds, or
55+70 = 125 mph.
To get 440 miles apart, it will take (440-35)/125 hours.
t = 405/125 = 3.24 hours.
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Cell phones do not have a distance range. They're called cell phones because the area (city, neighborhood, etc) is divided into cells, and the phones use an antenna on a tower within the cell where it's located.
As you drive, your phone's presence is detected by the nearest cell, based on either triangulation or signal strength, and communication with the cell you left is terminated. The closer antenna then becomes your link to the system.
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