Răspuns: 30 km/h
Explicație:
average speed = total distance : total elapsed time
total distance = 100 m
total elapsed time = 12 s
average speed = 100 m : 12 s = 8,3333 m/s
one hour = 3600 s
average speed = 8,3333 m/s x 3600 s / h = 30 000 m/h = 30 km/h