Final answer:
Noreen's average speed is calculated by multiplying the time it takes to walk 1/3 mile by 3 to get the time for 1 mile, then converting minutes to hours and using the formula for average speed. Her average speed is 1.67 miles per hour.
Step-by-step explanation:
To calculate Noreen's average speed in miles per hour, we first determine how many hours it takes for her to walk 1 mile given her current rate. Since it takes her 12 minutes to walk 1/3 mile, we multiply 12 minutes by 3 to find out how long it takes her to walk a full mile, which is 36 minutes. To convert this to hours, we divide 36 minutes by 60 minutes per hour, getting 0.6 hours.
To find the average speed (S), we use the formula S = distance / time. Noreen walks 1 mile in 0.6 hours, so her average speed is 1 mile / 0.6 hours = 1.67 miles per hour.