SOLUTION: On a recent road trip, you drove 90 miles at a constant rate. If you would have driven 15 miles per hour faster, your travel time would have been reduced by 0.5 hours. What was you
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Question 1047675: On a recent road trip, you drove 90 miles at a constant rate. If you would have driven 15 miles per hour faster, your travel time would have been reduced by 0.5 hours. What was your original rate? Answer by ewatrrr(24785) (Show Source):
You can put this solution on YOUR website! distance the same: D = rt, t = 90/r originally
(r+15)(90/r - .5) = 90
90 + 15*90/r-.5r - .5*15 = 90
15*90/r-.5r - .5*15 = 0
15*90 - .5r^2 - 7.5r = 0
30*90 - r^2 -15r = 0
r^2 + 15r - 2700 = 0
(r+60)(r-45)=0
r = 45mph, original speed
