How many cars does a train carry?

This depends entirely upon the cargo. Passenger trains may have between two and eight cars, depending upon the location and country. At the other extreme are the coal trains of Australia which can easily carry in excess of forty cars.

If the question refers to actual cars - as in the vehicles - that a train can transport, it will depend on how many locomotives are used, but if the train is hauling forty carriages (also called cars) and each car carries one car, that is an easy forty cars.