document.write( "Question 147112: Alan and Dave leave from the same point driving in opposite directions, Alan driving at 55 miles per hour and Dave 65 mph. Alan has a one hour head start. How long will they be able to talk on their car phones if the phones have a 250-mile range? \n" ); document.write( "

Algebra.Com's Answer #107452 by giveback(3) $\"\"$ $\"About$

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Let t (in hour) is the time Alan and Dave can talk on their car phone.
\n" ); document.write( "Because they are driving from the same starting point but in opposite directons then after t hour, Alan's distance from the start is 55t.
\n" ); document.write( "Meanwhile Dave only starts driving 1 hour after Alan, therefore after t hour, Dave's distance from the start is 65(t-1).
\n" ); document.write( "The combined distance should be equal or smaller than 250 miles.
\n" ); document.write( "From that, we have: 55t+65(t-1)=250 or 55t+65t-65=250 or 120t=315
\n" ); document.write( "Then t=315/120 or t=2 hours and (75/120)hour which is 2 hours and 37.5 minutes.
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