Motion problem - please show all work

Question

A railway track is parallel to a road. A school bus driver is riding his bus at a speed of 60km/h. The bus driver notices a tarin, 125m long, coming in the opposite direction and it passes his bus in 3 seconds. What is the speed if the train.

Answer 1

Neglecting the length of the bus, we can use relative motion. The combined speed of bus and train is v+60 km/hr, where v is the train speed. 125m is 0.125km. The time in hours taken for the train to pass the bus (driver) is 0.125/(v+60)=3/3600 hr. So 450=3(v+60); 3v=450-180=270, making v=90km/hr.