Final answer:
To find the average rate of speed, calculate the total distance traveled and the total time taken. Divide the total distance by the total time to get the average rate of speed, which is 65.625 miles per hour.
Step-by-step explanation:
To find the average rate of speed, we need to calculate the total distance traveled and the total time taken.
Bette drives at 60 miles per hour for 2 1/2 hours, which is a distance of 150 miles. She then drives at 75 miles per hour for 1 1/2 hours, which is a distance of 112.5 miles.
The total distance traveled is 150 miles + 112.5 miles = 262.5 miles.
The total time taken is 2 1/2 hours + 1 1/2 hours = 4 hours.
To calculate the average rate of speed, we divide the total distance by the total time: 262.5 miles / 4 hours = 65.625 miles per hour.