SOLUTION: A car traveled 1280 miles at a certain speed. If the speed had been 16 mph faster, the trip could have been made in 4 hours less time. what was the speed?

Question 734020: A car traveled 1280 miles at a certain speed. If the speed had been 16 mph faster, the trip could have been made in 4 hours less time. what was the speed?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
A car traveled 1280 miles at a certain speed. If the speed had been 16 mph faster, the trip could have been made in 4 hours less time. what was the speed?
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Slower trip DATA:
distance = 1280 miles ; speed = x mph ; time = d/r = 1280/x hrs
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Faster trip DATA:
distance = 1280 miles ; speed = x+16 mph ; time = d/r = 1280/(x+16) hrs
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Equation:
time - time = 4 hrs
1280/x - 1280/(x+16) = 4 hrs
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1280*16 = 4x(x+16)
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1280*4 = x^2+16x
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x^2 + 16x - 5120 = 0
Factor:
(x-64)(x+80) = 0
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Positive solution:
x = 64 mph
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Cheers,
Stan H.
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