Final answer:
Dividing the distance John travels to the concert by his average speed gives the time interval it takes him to reach there, which is the formula used to calculate time when distance and speed are known.
Step-by-step explanation:
When you divide the distance John travels to the concert by his average speed for the entire trip, you are calculating the time interval it takes him to reach his destination. The formula for calculating average speed is the total distance traveled divided by the total time of travel. Since you're dividing distance by speed to find time, answer choice (c) time interval is correct. It is essential to distinguish that speed is the rate of change of distance with respect to time, time interval is the duration of the journey, and distance is the length of the path taken. Understanding these concepts is fundamental when dealing with problems regarding motion, and they are especially useful when you're figuring out travel plans, like in John's case.