i don't know the answer but this can help
Two cars leave town at the same time travelling in the same direction.
One travels 80 km/h and the other 100 km/h. In how many hours will they be 90 km apart?
Answer by ikleyn(11788) (Show Source):You can put this solution on YOUR website!
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The distance between the cars increases at the rate of 100 - 80 = 20 km/h.
Therefore, in = 4.5 hours = 4 hours and 30 minutes the distance between the cars will be 90 km/h.