document.write( "Question 150888: 3. Steve traveled 600 miles at a certain speed. Had he gone 20mph faster, the trip would have taken 1 hour less. Find the speed of his vehicle. \n" ); document.write( "

Algebra.Com's Answer #110833 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
Let Steve's speed = $\"r\"$
\n" ); document.write( " $\"d+=+r%2A+t\"$
\n" ); document.write( " $\"600+=+r%2At\"$
\n" ); document.write( " $\"t+=+600+%2F+r\"$
\n" ); document.write( " $\"600+=+%28r+%2B+20%29%2A%28t+-+1%29\"$
\n" ); document.write( " $\"600+=+%28r+%2B+20%29%2A%28%28600%2Fr%29+-+1%29\"$
\n" ); document.write( " $\"600+=+600+%2B+12000%2Fr+-+r+-+20\"$
\n" ); document.write( "Subtract $\"600\"$ from both sides
\n" ); document.write( " $\"0+=+12000%2Fr+-+r+-+20\"$
\n" ); document.write( "multiply both sides by $\"r\"$
\n" ); document.write( " $\"-r%5E2+-+20r+%2B+12000+=+0\"$
\n" ); document.write( "Use quadratic formula to solve
\n" ); document.write( " $\"r+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\"$
\n" ); document.write( "

\n" ); document.write( " $\"r+=+%2820+%2B-+sqrt%2848400+%29%29%2F-2%29+\"$
\n" ); document.write( " $\"r+=+%2820+%2B-+220%29%2F-2%29+\"$
\n" ); document.write( " $\"r+=+-10+%2B+110\"$
\n" ); document.write( " $\"r+=+-10+-+110\"$
\n" ); document.write( " $\"r+=+100\"$
\n" ); document.write( " $\"r+=+-120\"$ reject this answer- can't be negative
\n" ); document.write( "His speed is 100 mi/hr
\n" ); document.write( "check answer:
\n" ); document.write( " $\"600+=+%28r+%2B+20%29%2A%28%28600%2Fr%29+-+1%29\"$
\n" ); document.write( " $\"600+=+%28100+%2B+20%29%2A%28%28600%2F100%29+-+1%29\"$
\n" ); document.write( " $\"600+=+120%2A%286+-+1%29\"$
\n" ); document.write( " $\"600+=+120%2A5\"$
\n" ); document.write( " $\"600+=+600\"$
\n" ); document.write( "OK \n" ); document.write( "

\n" );