Final answer:
Ricardo's average rate in miles per hour is 45 miles per hour.
Step-by-step explanation:
To find Ricardo's average rate in miles per hour, we need to convert the time from minutes to hours and divide the distance by the converted time.
First, let's convert the time: 20 minutes = 20/60 = 1/3 hours.
Then, we can calculate the average rate by dividing the distance (15 miles) by the time (1/3 hours):
average rate = distance / time = 15 miles / (1/3) hours = 15 miles * 3 = 45 miles per hour.