document.write( "Question 1086475: Two planes make a 1680 mile flight, one flying 10 miles per hour faster than the other. The quicker plane makes the trip 4 hours faster. How long did it take the slower plane to complete the flight? \n" ); document.write( "
Algebra.Com's Answer #700684 by josgarithmetic(39620)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "                 SPEED     TIME          DISTANCE\r\n" );
document.write( "Fast Plane       r+10     1680/(r+10)     1680\r\n" );
document.write( "Slow Plan         r       1680/r          1680\r\n" );
document.write( "Difference                 4\r\n" );
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\r
\n" ); document.write( "\n" ); document.write( "\"1680%2Fr-1680%2F%28r%2B10%29=4\"\r
\n" ); document.write( "\n" ); document.write( "-\r
\n" ); document.write( "\n" ); document.write( "\"420%2Fr-420%2F%28r%2B10%29=1\"\r
\n" ); document.write( "\n" ); document.write( "\"420%28r%2B10%29-420r=r%5E2%2B10r\"
\n" ); document.write( "\"420r%2B4200-420r=r%5E2%2B10r\"
\n" ); document.write( "\"4200=r%5E2%2B10r\"
\n" ); document.write( "\"r%5E2%2B10r-4200=0\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "discrim, \"100%2B4%2A4200=16900=10%5E2%2A13%5E2=130%5E2\"\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "\"r=%28-10%2B130%29%2F2\"\r
\n" ); document.write( "\n" ); document.write( "\"highlight_green%28r=60%29\"\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Slower Plane: \"1680%2F60=highlight%2828%29\", hours
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