document.write( "Question 139112: Loren drove 200 miles at a certain rate and his wife Lois drove 100 miles at a rate 10 mph slower. If loren had driven the entire trip they would have arrived 30 minutes sooner What was Loren's rate. \n" ); document.write( "
Algebra.Com's Answer #101534 by ankor@dixie-net.com(22740)\"\" \"About 
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Loren drove 200 miles at a certain rate and his wife Lois drove 100 miles at a rate 10 mph slower. If loren had driven the entire trip they would have arrived 30 minutes sooner What was Loren's rate.
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\n" ); document.write( "Let s = Lor rate of speed
\n" ); document.write( "then
\n" ); document.write( "(s-10) = Loi's rate of speed
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\n" ); document.write( "Write a time equation: Time = dist/speed
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\n" ); document.write( "Lor time + .5 hr = Lor's + Loi's time
\n" ); document.write( "\"300%2Fs\" + .5 = \"200%2Fs\" + \"100%2F%28%28s-10%29%29\"
\n" ); document.write( "Multiply equation by s(s-10) to get rid of the denominators
\n" ); document.write( "s(s-10)*\"300%2Fs\" + .5s(s-10) = s(s-10)*\"200%2Fs\" + s(s-10)*\"100%2F%28%28s-10%29%29\"
\n" ); document.write( "Cancel out the denominators and you have:
\n" ); document.write( "300(s-10) + .5s^2 - 5s = 200(s-10) + 100s
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\n" ); document.write( "300s - 3000 + .5s^2 - 5s = 200s - 2000 + 100s
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\n" ); document.write( "group like terms on the left:
\n" ); document.write( ".5s^2 + 300s - 5s - 200s - 100s - 3000 + 2000 = 0
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\n" ); document.write( ".5s^2 - 5s - 1000 = 0
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\n" ); document.write( "Multiply eq by 2, to make the coefficient of s^2 = 1
\n" ); document.write( "s^2 - 10s - 2000 = 0
\n" ); document.write( "Factor
\n" ); document.write( "(s-50)(s+40) = 0
\n" ); document.write( "Positive solution:
\n" ); document.write( "s = +50 mph is Lore's speed
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\n" ); document.write( "Check solution by finding the times:
\n" ); document.write( "200/50 + 100/40 = 6.5 hrs
\n" ); document.write( "300/50 = 6 hrs
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