document.write( "Question 1128494: I did this wrong twice and I am on my final chance to get it right; can someone please assist. Thank you.\r
\n" ); document.write( "\n" ); document.write( "A car travels 560 mi averaging a certain speed. If the car had gone 10 mph faster, the trip would have taken 1 hr less. Find the car's average speed. \n" ); document.write( "

Algebra.Com's Answer #744963 by ikleyn(52781) $\"\"$ $\"About$

You can put this solution on YOUR website!
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document.write( "Let x be the car average speed.\r\n" );
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document.write( "Theт the time for the trip is  hours.\r\n" );
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document.write( "Had the car moved 10 mph faster, its speed would be (x+10) mph and the time for the trip would be  hours.\r\n" );
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document.write( "The condition says that\r\n" );
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document.write( "     -  = 1  hour.     (1)\r\n" );
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document.write( "The number 560 has two remarcable divisors 70 and 80 that differ by 10.\r\n" );
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document.write( "It gives me an idea that x= 70.\r\n" );
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document.write( "Check.   -  = 8 - 7 = 1.\r\n" );
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document.write( "So, the answer is:  the car' speed under the question is  70 mph.\r\n" );
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document.write( "Surely, it is my guess ( ! the correct and checked guess, though !).\r\n" );
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document.write( "But you can solve the equation (1) algebraically, too.\r\n" );
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document.write( "For it, multiply both its sides by  x*(x+10).\r\n" );
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document.write( "You will get a quadratic equation\r\n" );
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document.write( "   560*(x+10) - 560x = x*(x+10),\r\n" );
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document.write( "    x^2 + 10x - 5600 = 0.\r\n" );
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document.write( "Factor the left side polynomial\r\n" );
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document.write( "    (x-70)*(x+80) = 0.\r\n" );
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document.write( "Only positive root  x= 70  is meaningful.\r\n" );
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document.write( "Thus we completed the algebraic solution, and got THE SAME answer:  the averaged speed of the car is 70 miles per hour.\r\n" );
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\n" ); document.write( "\n" ); document.write( "Solved.\r
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\n" ); document.write( "\n" ); document.write( "Is everything clear to you in my post ?\r
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\n" ); document.write( "\n" ); document.write( "You may find other similar solved problems in the lessons\r
\n" ); document.write( "\n" ); document.write( " - Selected Travel and Distance problems from the archive \r
\n" ); document.write( "\n" ); document.write( " - Had a car move faster it would arrive sooner\r
\n" ); document.write( "\n" ); document.write( "in this site.\r
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