Write a task of actions. from two cities removed from each other on 1680 km. there were at the same time towards each other 2 trains. The first train passes all this distance in 21 hour, and the second train in 28 hours in how many hours of the train will meet

97
We learn speeds of trains 1) 1680:21=80km/h the speed of 1 train 2) 1680:28=60km/h speed 2 trains 3) 80+60=140km/h the speed of rapprochement 4) 1680:140=12ch the answer of 12 h
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