There is a train which is 100 km in length and is going at 100km/h. The train is about to go through a tunnel which is exactly 100 km in length.
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How long is it, until the train completely passes through and comes out of the tunnel?
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1.5 hours
2.5 hours
4 hours
1 hour
2 hours

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The tunnel length is 100km The length of the train is also 100km.

Speed of the train is 100km/h. (it means the train will travel 100kms in 1 hour).

Therefore, when the engine passes the tunnel, its 1 hour, but the train is itself also another 100 km long So, in this case the total time taken by the complete train to leave the tunnel = (length of tunnel + length of the train ). = (100 + 100) km. speed = 100 km/h. time taken = (200/100) = 2h.