Question 903540: 1.) A jet plane, flying 120 mph faster than a propeller plane, travels 5760 miles in 4 hours less time than the propeller plane takes to fly the same distance. How fast does each plane fly?
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! 1.) A jet plane, flying 120 mph faster than a propeller plane, travels 5760 miles in 4 hours less time than the propeller plane takes to fly the same distance. How fast does each plane fly?
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Prop distance:: r(t+4)
Jet distance:: (r+120)t
rt+4r = rt + 120t
r = 30t
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Jet DATA:
distance = 5760 miles ; rate = x+120 mph ; time = d/r = 5760/(x+120)
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Prop DATA::
distnce = 5760 miles ; rate = x mph ; time = d/r = 5760/x
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Equation::
time - time = 4
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prop time - jet time = 4 hrs
5760/x - 5760/(x+120) = 4
120*5760 = 4x(x+120)
30*5760 = x^2 + 120x
x^2+120x-30*5760 = 0
(x-360)(x+480) = 0
Positive solution::
x = 360 mph (prop plane speed)
x+120 = 480 mph (jet plane speed)
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Cheers,
Stan H.
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