SOLUTION: two trains leave a station at the same time, heading in opposite directions. One train is traveling at 80 km/h, the other at 90 km/h. how long will it take for the trains to be 4

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Question 173493: two trains leave a station at the same time, heading in opposite directions. One train is traveling at 80 km/h, the other at 90 km/h. how long will it take for the trains to be 425 km apart?
Found 2 solutions by vleith, gonzo:
Answer by vleith(2983) (Show Source):
You can put this solution on YOUR website!
They are moving away from each other at (80+90) or 170km/h
ow long does it take to go 425km at 170km/hr?
425/170= 2.5 hours

Answer by gonzo(654) (Show Source):
You can put this solution on YOUR website!
total distance traveled by both trains is 425 miles in total (distance traveled by train A + distance traveled by train B).
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the time it takes for them both to travel a total of 425 miles is T hours.
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the total rate that they travel is 170 kmph (80 kmph in one direction and 90 kmph in the other direction).
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since rate * time = distance and:
rate = 170kmph
time = T
distance = 425 km
then equation is:
(80 + 90)*T = 425
which becomes:
170*T = 425
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divide both sides by 170 to get:
T = 425/70 = 2.5
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total time taken by both trains simultaneously is 2.5 hours
train A travels for 2.5 hours at 80 kmph for a total distance of 200 km.
train B travels for 2.5 hours at 90 kmph for a total distance of 225 km.
total distance traveled by both is 425 km.
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answer is:
it will take the trains 2.5 hours to be 425 km apart.