document.write( "Question 73763: Jeff starts driving at 75 miles per hour from the same point that Lauren starts driving at 70 miles per hour. They drive in opposite directions, Lauren has a half-hour head start. How long will they be able to talk on their cell phones that have a 370-mile range? \n" ); document.write( "
Algebra.Com's Answer #52747 by bucky(2189)\"\" \"About 
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Let t be the time that Jeff drives. Then the time that Lauren drives is t + 1/2 hour.
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\n" ); document.write( "The basic equation we will be using is Distance = Rate * Time
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\n" ); document.write( "The distance Lauren covers has a rate of 70 mph and a time of (t + 1/2) so her distance is
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\n" ); document.write( "D = r*t = 70*(t + 1/2) = 70*t + 35
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\n" ); document.write( "Jeff drives for time t at a rate of 75 mph. So Jeff's distance is:
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\n" ); document.write( "D = r*t = 75*t
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\n" ); document.write( "When the sum of these two distances equals 370 miles, Jeff and Lauren's cell phones will
\n" ); document.write( "stop operating. So we can set up the equation:
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\n" ); document.write( "70*t + 35 + 75t = 370
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\n" ); document.write( "Adding the terms containing t results in:
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\n" ); document.write( "145*t + 35 = 370
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\n" ); document.write( "Eliminate the 35 on the left side by subtracting 35 from both sides to get:
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\n" ); document.write( "145*t = 370 - 35 = 335
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\n" ); document.write( "Solve this equation by dividing both sides by 145 to find that:
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\n" ); document.write( "t = 335/145 = 2.310 hours
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\n" ); document.write( "which is about 2 hours and 19 minutes \n" ); document.write( "
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