SOLUTION: During rush hour, Fernando can drive 20 miles using the side roads in the same time that it takes to travel 15 miles on the freeway. If Fernando's rate on the side roads is 9 mi/h

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: During rush hour, Fernando can drive 20 miles using the side roads in the same time that it takes to travel 15 miles on the freeway. If Fernando's rate on the side roads is 9 mi/h      Log On


   

Question 91244: During rush hour, Fernando can drive 20 miles using the side roads in the same time that it takes to travel 15 miles on the freeway. If Fernando's rate on the side roads is 9 mi/h faster than his rate on the freeway, find his rate on the side roads.
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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During rush hour, Fernando can drive 20 miles using the side roads in the same time that it takes to travel 15 miles on the freeway. If Fernando's rate on the side roads is 9 mi/h faster than his rate on the freeway, find his rate on the side roads.
:
let s = speed on side roads
then
(s-9) = speed on the freeway
:
Write a time equation: Time = Dist/speed
Sideroad time = Freeway time
20%2Fs = 15%2F%28%28s-9%29%29
:
Cross multiply
20(s-9) = 15s
:
20s - 180 = 15s
:
20s - 15s = +180
:
5s = 180
:
s = 180/5
:
s = 36 mph speed on the side-roads
:
:
Check solution using the time
20/36 = 5/9
15/27 = 5/9