Answer
Olga had the fastest average speed.
Work Step by Step
In order to find average speed, we divide the total distance traveled by the amount of time it took to travel that distance. Thus, we obtain:
Trisha: $10km/2.5 hours=4$ km per hour
Olga: $9.5km / 2.25 hours=4.22$ km per hour
Jason: $ 7.5km/2 hours=3.75$km per hour
Thus, we find that Olga had the fastest average speed.
