Final answer:
Marcy's speed was 8 miles per hour. She rode a total distance of 4 miles in 30 minutes around a 1/4 mile track, and after converting the time to hours, you can calculate the speed by dividing distance by time.
Step-by-step explanation:
To calculate Marcy's speed in miles per hour, we need to know the total distance she rode and the total time it took. Marcy rode her bike around a 1/4 mile track 16 times, so we can calculate the distance covered:
- Distance per lap = 1/4 mile
 - Number of laps = 16
 - Total distance = Distance per lap × Number of laps = 1/4 mile × 16 = 4 miles
 
Marcy took 30 minutes to cover this distance. To find the speed in miles per hour, we need to convert the time into hours:
- Time in hours = 30 minutes ÷ 60 minutes/hour = 0.5 hour
 
Speed is calculated by dividing the total distance by the total time:
- Speed = Total distance ÷ Time in hours = 4 miles ÷ 0.5 hour = 8 miles/hour
 
Hence, Marcy's speed was 8 miles per hour.