SOLUTION: During rush hour, Adriana can drive 30 miles using the side roads in the same time that it takes to travel 15 miles on the freeway. If Adriana''s rate on the side roads is 6 mi/h f

Algebra ->  Problems-with-consecutive-odd-even-integers -> SOLUTION: During rush hour, Adriana can drive 30 miles using the side roads in the same time that it takes to travel 15 miles on the freeway. If Adriana''s rate on the side roads is 6 mi/h f      Log On


   

Question 76289: During rush hour, Adriana can drive 30 miles using the side roads in the same time that it takes to travel 15 miles on the freeway. If Adriana''s rate on the side roads is 6 mi/h faster than her rate on the freeway, find her rate on the side roads.
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
During rush hour, Adriana can drive 30 miles using the side roads in the same time that it takes to travel 15 miles on the freeway. If Adriana''s rate on the side roads is 6 mi/h faster than her rate on the freeway, find her rate on the side roads.
:
Let s = speed on the side road. Let (s-6) = speed on the freeway
:
Write a time equation, Time = Distance/Speed
:
Side road time = Freeway time
30%2Fs%29 = 15%2F%28%28s-6%29%29
:
Cross multiply:
30(s-6) = 15s
30s - 180 = 15s
30s - 15s = 180
15s = 180
s = 180/15
s = 12 mph on the side road
:
That seems awful slow, check the times on both speeds, 12 mph and 6 mph:
30/12 = 2.5 hrs
15/6 = 2.5 hrs; must be right!