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It took a train 20 seconds to completely pass a 500-m iron bridge. When the train was passing through a 1900-m tunnel, it was invisible from outside of the tunnel for 30 seconds. If the speed of the train was constant, what was the length of the train (in meters)?

 Aug 5, 2020
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We can use algebra s=speed and l=length (500+l)/s=20, (1900-l)/s=30 we have that s=48 and l=460 by Adding the equations in order to solve for the first variable. Then we plug this value into the other equations in order to solve for the remaining variables. 

 

so we have the \(\text{speed}=48,\text{ and }\boxed{\text{length of the train}=460m}\)

 Aug 5, 2020

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