document.write( "Question 1145951: Imogene's car traveled 660 mi averaging a certain speed. If the car had gone 6 mph faster, the trip would have taken 1 hour less. Find the average speed. \n" ); document.write( "

Algebra.Com's Answer #767215 by ikleyn(52781) $\"\"$ $\"About$

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document.write( "Let x be the average speed under the question.\r\n" );
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document.write( "Then the travel time for 660 miles distance is   hours.\r\n" );
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document.write( "The hypothetical travel time is    hours.\r\n" );
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document.write( "The difference is 1 hour :\r\n" );
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document.write( "     -  = 1  hour.\r\n" );
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document.write( "It is your basic equation, the \"time\" equation.\r\n" );
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document.write( "To solve it, multiply both sides by x*(x+6).  You will get\r\n" );
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document.write( "    660*(x+6) - 660x = x*(x+6).\r\n" );
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document.write( "Simplify and solve for x\r\n" );
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document.write( "    660*6 = x^2 + 6x\r\n" );
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document.write( "    x^2 + 6x - 3960 = 0\r\n" );
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document.write( "     =  = .\r\n" );
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document.write( "Only positive root makes sense  x =  = 60.\r\n" );
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document.write( "ANSWER.  The average speed under the question is 60 miles per hour.\r\n" );
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document.write( "CHECK.   = 11 - 10 = 1 hour.  ! Precisely correct \r\n" );
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