From two cities, the distance between which is 420 km, two trains left simultaneously towards each other.

From two cities, the distance between which is 420 km, two trains left simultaneously towards each other. The meeting took place 3 hours later. The speed of the first train is 72 km / h. How fast was the second train?

The solution of the problem:
At the same time, two trains left the two cities to meet each other. Three hours later, they met. The speed of the first train is known. Let’s calculate the number of kilometers covered by the first train in 3 hours.
3 * 72 = 216 kilometers.
Let’s find how many kilometers the second train traveled before the meeting.
420 – 216 = 204 kilometers.
Let’s calculate how fast the second train was moving.
204: 3 = 68 km / h
Answer: Before the meeting, the second train was moving at a speed of 68 km / h.