SOLUTION: Really stumped on this one!!! A bike is rode 15 miles up a hill and then 15 miles back down the same hill. The total trip takes 2 hours. If the speed going downhill is 20 mph

Question 524416: Really stumped on this one!!!
A bike is rode 15 miles up a hill and then 15 miles back down the same hill. The total trip takes 2 hours. If the speed going downhill is 20 mph faster than going uphill, how fast is the ride uphill?
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
You need 2 equations: 1 for uphill and
1 for downhill
mi is the same for both trips
Let = the time to go uphill in hrs
is the speed going downhill in hrs
Let = the speed going uphill
is the speed going downhill
----------------------------
Going uphill:
(1)
Going downhill:
(2)
-----------------------
(2)
(2)
Substitute (1) into (2)
(2)
(2)
-----------------
(1)
(1)
Substitute this into (2)
(2)
(2)
(2)
(2)
Using the quadratic formula:

( can't use the negative root )

The ride uphill is 10 mi/hr
check:
(1)
(1)
(1) hrs
and
(2)
(2)
(2)
(2)
(2)
(2)
(2) hrs
OK
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