Final answer:
Sally's average speed, excluding the time spent talking with a friend, is calculated as the total distance (2 km) divided by the total walking time (25 minutes or 0.4167 hours), leading to an average speed of 4.8 km/h, which is not among the provided options.
Step-by-step explanation:
To calculate Sally's average speed for her entire walk, we first need to determine the total time she spent walking. Sally walked for 15 minutes, spoke with her friend for 10 minutes, and then continued walking for another 10 minutes. This results in a total walking time of 25 minutes. However, as the time she spent talking to Tori is not included in the time she was moving, we do not count the 10 minutes of conversation towards calculating her average speed.
To find the average speed, we use the formula:
Average speed = Total distance / Total time taken
The total distance Sally walked is 2 km. To convert 25 minutes to hours (since speed is usually expressed in km/h), we divide 25 by 60, which gives us approximately 0.4167 hours.
Thus, Sally's average speed is:
Average speed = 2 km / 0.4167 hours = 4.8 km/h
However, this is not one of the options given. It appears there may be an error in the provided answer choices. A more accurate choice closest to our calculation would be an option not provided in the question.