document.write( "Question 1175669: On some highways, a car can legally travel 20 km/hr faster than a truck.\r
\n" ); document.write( "\n" ); document.write( "Travelling at maximum legal speeds, a car can travel 120 kms in 18 minutes less than a truck.\r
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Algebra.Com's Answer #801328 by ikleyn(52879) $\"\"$ $\"About$

You can put this solution on YOUR website!
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document.write( "The time equation is\r\n" );
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document.write( "     -  =  =   of an hour.\r\n" );
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document.write( "To solve it, multiply both sides by x*(x-20).  You will get\r\n" );
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document.write( "    1200x - 1200(x-20) = 3x*(x-20)\r\n" );
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document.write( "        24000 = 3x*(x-20)\r\n" );
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document.write( "         8000 = x*(x-20)      (*)\r\n" );
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document.write( "At this point, you just can guess the solution  x= 100.\r\n" );
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document.write( "ANSWER.  the maximum speed is  100 km/h for cars and 80 km/h for trucks.\r\n" );
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document.write( "CHECK.    -  =  =  =  =  =  of an hour = 18 minutes.  ! Correct !\r\n" );
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\n" ); document.write( "\n" ); document.write( "Instead of guessing, you may solve equation (*) formally . . . \r
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