Question 1192299
A freight train left the main station heading east at average speed of 100kph. An hour later an express train left the same station heading west at an average of 170kph. At what time will they be 600kms apart from each other? 
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At what time will they be 600kms apart? ========  from each other? 
"from each other" is not needed.
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After one hour, the freight train is 100 kms from the station.
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Going in opposite directions, their speeds are added ---> 270 km/hr.
The time to be another 500 kms apart = 500/270 hours
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The starting time was not given, so there's no way to know what time they will be 600 kms apart.