From two towns A and B, with distance 300km between them, at the same time left two trains. We know that the speed of one of the trains is with 10km/h faster than the speed of the other one. Find the speed of the two trains if 2 hours after their departure the distance between them is 40km. Solution Lets take the speed of the slower train as x km/h.The speed of the other will be x + 10 km/h. After 2 hours they will cross 2x km and 2 9x +10) km.Then the whole distance from A to B is 2x + 2(x +10) +40 = 4x +60 km, if the trains hasn’t already met or 2x +2( x +10) -40 = 4x -20 km, if they have met. So we get the following two equations: 4x + 60 = 300 <=> 4x = 240 <=> x = 60 or 4x – 20 = 300 <=> 4x = 320 <=> x = 80 So the speed of the slower train is 60 km/h or 80 km/h and the speed of the other one is 70 km/h or 90 km/h.