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

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