SOLUTION: Madisson drove to Nashville and back and spent a total of 8 hours of driving. She drove at a certain speed on the trip down, but she averaged 40km/h faster on her return tri

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: Madisson drove to Nashville and back and spent a total of 8 hours of driving. She drove at a certain speed on the trip down, but she averaged 40km/h faster on her return tri      Log On


   



Question 887707: Madisson drove to Nashville and back and spent a total of 8 hours of driving. She drove at a
certain speed on the trip down, but she averaged 40km/h faster on her return trip. If the total trip
was 600km, how fast did she drive back from Nashville?

Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
Let r = the certain speed going.
________________rate_______time________distance
NASHVILLE_______r
BACK FROM_______r+40
TOTAL_______________________8___________600

The question asks for r+40 but you want to solve for r first (the way the variables were here assigned).

RT=D for rate time distance, so T and D can be found accordingly.

________________rate_______time________distance
NASHVILLE_______r___________x__________rx
BACK FROM_______r+40_______8-x______(r+40)(8-x)
TOTAL_______________________8___________600
Not seeing any progress with that chart.

________________rate_______time________distance
NASHVILLE_______r__________x___________rx
BACK FROM_______r+40________y________(r+40)y
TOTAL_______________________8___________600
-
This gives only two equations but three unknowns.
------------------------
x%2By=8
rx%2Bry%2B40y=600
------------------------
The "600" equation is also r%28x%2By%29%2B40y=600
r%2A8%2B40y=600
r%2B5y=75

This would seem to give a system:
----------
highlight_green%28x%2By=8%29
-
highlight_green%28r%2B5y=75%29
----------

Which could have more than one solution.