A runner can run a 400.0 meter lap in 50.0 seconds. He finishes at the same spot as he began. What is his average velocity?

Answer 1

velocity is a vector, not a scalar
to measure speed, use a speedometer
to measure velocity yo need both a speedometer AND a compass.
It you go around a circle, you go the same distance in every direction
whatever your speedometer reads, you came back to the same spot
so your displacement was ZERO
V average = ZERO