A train crosses a bridge of length 1500 m in 70 seconds and a lamp post on the bridge in 20 seconds. What is the length of the train in metres?	Choose the correct choice from the following answers
A) 375 m  B) 750 m  C) 250 m  D) 600 m  E) 300 m
Let Length of Train = L   Case-1: Distance = 1500+L (While crossing the bridge)   Time = 70 Seconds   i.e. Speed = Distance / Time = (1500+L)/70   Case-2: Distance = L (While passing the lamp post)   Time = 20 Seconds   i.e. Speed = Distance / Time = (L)/20   But Since speed has to be same in both cases so   (1500+L)/70 = (L)/20   i.e. 1500 + L = 3.5 L   i.e. 2.5L = 1500   i.e. L = 600   Answer: option 600 m
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A train crosses a bridge of length 1500 m in 70 seconds and a lamp post on the bridge in 20 seconds. What is the length of the train in metres?