Average velocity is different than average speed because calculating average velocity involves considering the direction the bodies are moving.
When calculating average speeds you don't have to consider directions of the bodies.
This is because velocity is a vector quantity which must be defined by direction. Speed is a scalar quantity thus it does not have to be defined by direction.
From 200 BC to around 14 AD, Rome had conquered most of Western Europe, Greece and the Balkans. Also the Middle East, and North Africa.