# 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

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 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(9669)   (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