SOLUTION: A freight train covered 120 miles at a certain speed. Had the train been able to travel 10 mph faster, the trip would have been 2 hours shorter. How fast did the train go?

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Question 1027125: A freight train covered 120 miles at a certain speed. Had the train been able to travel 10 mph faster, the trip would have been 2 hours shorter. How fast did the train go?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
A freight train covered 120 miles at a certain speed. Had the train been able to travel 10 mph faster, the trip would have been 2 hours shorter. How fast did the train go?
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slower DATA:
dist = 120 miles ; rate = x mph ; time = 120/x hrs
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faster DATA:
dist = 120 miles ; rate = x+10 mph ; time = 120/(x+10) hrs
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Equation:
longer time - shorter time = 2hr
120/x - 120/(x+10) = 2 hr
120x + 120*10 - 120x = 2x(x+10)
2x^2 + 20x - 120*10 = 0
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x^2 + 10x - 600 = 0
x = 20 mph (slower rate)
x+10 = 30 (faster rate)
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Cheers,
Stan H.
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