Question 983846: A train takes 4sec to pass a telegraph post and 20sec to pass a 264m long bridge.let us find the length of train and also its speed. Found 2 solutions by macston, ikleyn:Answer by macston(5194) (Show Source):
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Consider the telegraph post at one end of the bridge.
To pass the bridge, the engine first goes on, and the train is not past the bridge until the rear goes off the other end. When the front passes the telegraph pole (goes on the bridge), 4 seconds pass before the rear goes on the bridge (passes the pole). The rear of the train must pass off the bridge 20 seconds after the engine goes on, or 16 seconds after the rear goes on (20 seconds-4 seconds for the whole train to pass the pole). The rear must travel 264m in 16 seconds, or 16.5 meters/second.
ANSWER: 1: The speed of the train is 16.5 meters per second.
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Traveling at 16.5m/s, it takes 4 seconds to pass the pole, so the length of the train is (4s)(16.5m/s)=66 meters.
ANSWER 2: The train is 66 meters long.
