SOLUTION: a passenger train leaves a train depot 2 hours after a freight train leaves the same depot. The freight train is traveling 20 mph slower than the passenger train. Find the rate of

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Question 352673: a passenger train leaves a train depot 2 hours after a freight train leaves the same depot. The freight train is traveling 20 mph slower than the passenger train. Find the rate of train if the passenger train overtakes the freight train in 3 hours.

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let the speed of the passenger train = s
How much of a head start did the freight train get?
Let d%5B1%5D = headstart
d%5B1%5D+=+%28s+-+20%29%2A2
d%5B1%5D+=+2s+-+40
Start a stopwatch when the passenger train leave depot
In 3 hours the freight train goes a distance of
d%5B2%5D+=+%28s+-+20%29%2A3
d%5B2%5D+=+3s+-+60
Now the passenger train must travel d+=+d%5B1%5D+%2B+d%5B2%5D
in 3 hours
s%2A3+=+2s+-+40+%2B+3s+-+60
2s+=+100
s+=+50
The speed of the passenger train is 50 mi/hr
check:
s+-+20+=+30
d%5B1%5D+=+%28s+-+20%29%2A2
d%5B1%5D+=+60
d%5B2%5D+=+%28s+-+20%29%2A3
d%5B2%5D+=+90
d%5B1%5D+%2B+d%5B2%5D+=+150 mi
3s+=+150
s+=+50
OK