Final answer:
The dependent quantity in the scenario where Sarah drives to the grocery store and back is the total time of her trip, which could be influenced by the time spent at the grocery store.
Step-by-step explanation:
In the context of Sarah's trip, the dependent quantity is a variable that depends on another variable, known as the independent quantity. For Sarah's trip to the grocery store and back, one possible dependent quantity could be the total time taken for the trip. This could be dependent on several factors such as the distance to the grocery store, the time spent at the grocery store, and the speed at which Sarah drives.
To identify the dependent quantity specifically from the information given, one could say that the time taken to drive back home is dependent on the time spent at the grocery store. Assuming Sarah took the same time to travel to the store and back, the total travel time from when she first left her house until returning would be dependent on the duration of her stay at the store.