SOLUTION: Afreight train and an express train leave towns 390km apart, traveling toward one another. The freight train travels 30km per hr slower than the express train. They pass another 3
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Question 60: Afreight train and an express train leave towns 390km apart, traveling toward one another. The freight train travels 30km per hr slower than the express train. They pass another 3 hr. later. What are their speeds!
Found 3 solutions by ichudov, noelsarrosa, amalm06:
Answer by ichudov(507) (Show Source): You can put this solution on YOUR website!
This is a typical travel problem. It asks us for their speeds, so, we need to find them! Denote speed of the express train as E, and speed of the freight train as F.
F=E-30
3*(F+E) = 390
OR
E-F=30
3E+3F = 390
it is a simple linear system, for which I have a solver that shows work.
Answer by noelsarrosa(1) (Show Source): You can put this solution on YOUR website!
(x-30+x)3=390
x-30+x=130
2x-30=130
2x=160
x=80, x-30=50
Checking:
(80+50)3=390
130(3)=390
390=390
Answer by amalm06(224) (Show Source): You can put this solution on YOUR website!
Distance traveled by express train: De/dt=r --> De=r dt (1)
Distance traveled by freight train: Df/dt=r-30 --> Df= r-30 dt (2)
Solve (1) and (2) as follows:
De = = 3r
Df = = 3r-90
The total distance traveled is 390 km:
3r+3r-90=390
6r-90=390
6r=480
r=80 km/hr, 50 km/hr (Answer)
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