How long will a passenger sitting at the window of a train traveling at a speed of 54 km / h

How long will a passenger sitting at the window of a train traveling at a speed of 54 km / h see a train passing by at a speed of 36 km / h and a length of 150 m?

Let’s take it as a reference system associated with a passenger. Then the speed of the oncoming train will be equal to:
54 + 36 = 90 km / h
let’s translate this speed from km / h to m / min:
90,000 / 60 = 1,500 m / min
To get an answer, it is enough to divide the length of the train by the found speed:
150/1500 = 0.1 min = 60 sec * 0.1 = 6 sec.