The speed of a freight train is 40 km / h less than that of a passenger train. A freight train takes 7 hours to travel

The speed of a freight train is 40 km / h less than that of a passenger train. A freight train takes 7 hours to travel the same way as a passenger train takes 4.2 hours. Find the speed of a freight train.

Let the speed of a freight train be x kilometers per hour, then the speed of a passenger train will be (x + 40) kilometers per hour. A freight train will cover 7 kilometers in seven hours, and a passenger train will travel 4.2 * (x + 40) kilometers in 4.2 hours, these distances are the same, we make an equation by equating them and find the speed of a freight train:
7x = 4.2 * (x + 40);
7x = 4.2x + 168;
7x – 4.2x = 168;
2.8x = 168;
x = 168: 2.8;
x = 60 (km / h).
Answer: a freight train moves at a speed of 60 kilometers per hour.