Question 349393: Dave is 1/3 of the way across the bridge when the sound of a train whistle brought him back to reality. Looking back over his shoulder he saw a huge locomotive pulling tons of box cars directly at him at 45 miles per hour. Using all of his powers of mathematical thought and analysis, Dave immediately figured tht he could run directly ahead and get to the far end of the bridge at the exact same time as the train. But he also knew that he could run back toward the train and get to the rear of the bridge just as the train got there. How fast does dave run?
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! Dave is 1/3 of the way across the bridge when the sound of a train whistle brought him back to reality.
Looking back over his shoulder he saw a huge locomotive pulling tons of box cars directly at him at 45 miles per hour.
Using all of his powers of mathematical thought and analysis, Dave immediately figured tht he could run directly ahead and get to the far end of the bridge at the exact same time as the train.
But he also knew that he could run back toward the train and get to the rear of the bridge just as the train got there.
How fast does dave run?
:
We can use logic here, Dave runs away from the train, we know that he will
have run 1/3 of the bridge when the train enters the opposite end.
That leaves 1/3 remaining for him to run while the train covers the whole dist of the bridge>
Another words, Dave runs 1/3 while the train runs 3/3 so he is running 1/3 * 45
Dave runs 15 mph
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