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)![]() ![]() You can put this solution on YOUR website! 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( ": \n" ); document.write( "Let s = Lor rate of speed \n" ); document.write( "then \n" ); document.write( "(s-10) = Loi's rate of speed \n" ); document.write( ": \n" ); document.write( "Write a time equation: Time = dist/speed \n" ); document.write( ": \n" ); document.write( "Lor time + .5 hr = Lor's + Loi's time \n" ); document.write( " \n" ); document.write( "Multiply equation by s(s-10) to get rid of the denominators \n" ); document.write( "s(s-10)* \n" ); document.write( "Cancel out the denominators and you have: \n" ); document.write( "300(s-10) + .5s^2 - 5s = 200(s-10) + 100s \n" ); document.write( ": \n" ); document.write( "300s - 3000 + .5s^2 - 5s = 200s - 2000 + 100s \n" ); document.write( ": \n" ); document.write( "group like terms on the left: \n" ); document.write( ".5s^2 + 300s - 5s - 200s - 100s - 3000 + 2000 = 0 \n" ); document.write( ": \n" ); document.write( ".5s^2 - 5s - 1000 = 0 \n" ); document.write( ": \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 \n" ); document.write( ": \n" ); document.write( ": \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 \n" ); document.write( " |