Final answer:
Arianna's speed was calculated to be 7.4 miles per hour by dividing the distance she ran (5.55 miles) by the time (0.75 hours).
Step-by-step explanation:
To find Arianna's speed in miles per hour, we use the formula for speed which is distance traveled divided by time taken. Arianna ran 5.55 miles in 0.75 hours. To calculate her speed, we divide the distance by the time:
Speed = Distance / Time
= 5.55 miles / 0.75 hours
= 7.4 miles per hour
Therefore, Arianna's speed was 7.4 miles per hour. This indicates that she was running at a speed that is just under the 40 percent of runners who ran at speeds of 7.5 miles per hour or less (slower).