SOLUTION: Kids are one third the way across a bridge when they hear the sound of a train whistle. They see a train coming toward them at 45 miles per hour. Kids figured out they could run

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Question 421658: Kids are one third the way across a bridge when they hear the sound of a train whistle. They see a train coming toward them at 45 miles per hour. Kids figured out they could run ahead to get to the far end of the bridge at the exact same time as the train or they could run back toward the train to the beginning of the bridge at the exact same time as the train arrived at the beginning of the bridge. How fast do the kids have to run to either make it to the beginning of the bridge at the same time as the train or to the end of the bridge at the same time as the train?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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Kids are one third the way across a bridge when they hear the sound of a train whistle.
They see a train coming toward them at 45 miles per hour. Kids figured out they
could run ahead to get to the far end of the bridge at the exact same time as
the train or they could run back toward the train to the beginning of the bridge
at the exact same time as the train arrived at the beginning of the bridge.
How fast do the kids have to run to either make it to the beginning of the
bridge at the same time as the train or to the end of the bridge at the same time as the train?
:
This is a thought problem.
Assume the kids run the same direction that the train is going.
From the information we know that the train will enter the bridge when the kids have run 1/3 of the way
So when the train enters the bridge, the kids are 1/3 way from the far end.
The trains covers the length of the bridge in the same some the kids cover 1/3 of the bridge.
therefore: kids run 1%2F3 * 45 = 15 mph