Can someone please help: Question: 2 cars are passing each other on opposite directions. One at 100 Km and the other at 150 Km. What is the passing speed?. I believe it is 0, however, I have been corrected that it is the combination of both, ie: 250 km. Or was the above question incomplete?. Would rate of separation be the same as passing speed?. If someone could explain to me and illustrate answer with formula, I would be very helpful. Thank you in advance.