document.write( "Question 453381: linda is going to visit a freind who lives in san luis obispo, which is 300 miles away. on the return trip, she was able to average 20 mi/hr faster, and it took her one hour and a quarter less time. what was her average speed on the way down, and what was her average speed on the way back.\r
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Algebra.Com's Answer #311506 by pedjajov(51)\"\" \"About 
You can put this solution on YOUR website!
On her way TO her friend Linda drove with:
\n" ); document.write( "r - speed
\n" ); document.write( "t - time it took her to her friend
\n" ); document.write( "d - 300mi, distance she passed
\n" ); document.write( ":
\n" ); document.write( "rt=d -> rt=300 -> r=300/t
\n" ); document.write( ":
\n" ); document.write( "On her way back Linda drove with:
\n" ); document.write( "r+20 - 20mi/h faster than on her way to friend
\n" ); document.write( "t-5/4 - she used 5/4 of the hour less time to travel
\n" ); document.write( "d - distance was the same 300 miles
\n" ); document.write( ":
\n" ); document.write( "(r+20)(t-5/4)=300
\n" ); document.write( "rt-5r/4+20t-25=300, multiply by 4
\n" ); document.write( "4rt-5r+80t-100=1200, substitute rt with 300 and r with 300/t
\n" ); document.write( "4*300-5*300/t+80t-100=1200, subtract 1200 from both sides
\n" ); document.write( "1200-1500/t+80t-100-1200=0, combine numbers
\n" ); document.write( "80t-1500/t-100=0, multiply by t
\n" ); document.write( "80t^2-100t-1500=0, divide by 20
\n" ); document.write( "4t^2-5t-75=0, solve using quadratic formula
\n" ); document.write( ":
\n" ); document.write( "\"t+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\"
\n" ); document.write( "\"t+=+%28-%28-5%29+%2B-+sqrt%28+%28-5%29%5E2-4%2A4%2A%28-75%29+%29%29%2F%282%2A4%29+\"
\n" ); document.write( "\"t+=+%285+%2B-+sqrt%28+25%2B1200%29%29%2F8+\"
\n" ); document.write( "\"t+=+%285+%2B-+35%29%2F8\"
\n" ); document.write( "\"t+=+%285%2B35%29%2F8+=+5\" or \"t=%285-35%29%2F8+=+3.75\"
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\n" ); document.write( "Only acceptable solution is positive number so t=5 hours on her way down.
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\n" ); document.write( "Her speed on the way down was 300/5 = 60mi/h.
\n" ); document.write( "Her speed on the way back was 60+20 = 80mi/h.\r
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