SOLUTION: A jogger has attempted to run across a railroad bridge, but sees a train coming after completing 3/4 of the trip. If the train is traveling at 30km/h, and if it is possible for the

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Question 1128955: A jogger has attempted to run across a railroad bridge, but sees a train coming after completing 3/4 of the trip. If the train is traveling at 30km/h, and if it is possible for the jogger to just escape being hit by the train by running at full speed to either end of the bridge, what is the minimum speed in km/h that this jogger must be able to run?
A)15 B)20 C)12 D)18 E)25
Answer by ankor@dixie-net.com(22740) (Show Source):
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A jogger has attempted to run across a railroad bridge, but sees a train coming after completing 3/4 of the trip.
If the train is traveling at 30km/h, and if it is possible for the jogger to just escape being hit by the train by running at full speed to either end of the bridge, what is the minimum speed in km/h that this jogger must be able to run?
:
We know the jogger will run 1/4 of the bridge just as the train enters the entrance to the bridge.
Going the other way he would also travel 1/4 of the way when the train enters the bridge.
That means he has 2/4 or 1/2 of the bridge to go just as the train enters the bridge.
He has to travel 1/2 of the bridge while the train travels the whole length.
therefore
His speed has to be: *30 = 15 km/hr
:
Did this make sense to you?