Final answer:
The bicyclist's average speed was calculated using the formula (total distance / total time), which equals 17.49 mph. The total distance was 78.7 miles, and the total time was 4.5 hours when converted from 4 hours and 30 minutes.
Step-by-step explanation:
To find the average speed of the bicyclist, we will use the formula:
average speed = total distance / total time
The total distance is given as 78.7 miles. The total time is 4 hours and 30 minutes. We need to convert 30 minutes into hours to have consistent units, so we divide 30 by 60, which gives us 0.5 hours. Therefore, the total time in hours is 4 + 0.5 = 4.5 hours.
Now, using the formula:
average speed = 78.7 miles / 4.5 hours = 17.49 mph
So, the bicyclist's average speed was 17.49 mph (option a).