Answer:
The time she left Chicago ⇒ answer A
Explanation:
* Lets explain the meaning of average speed
- The definition of the average speed is the average speed of an
object is defined as the distance traveled divided by the time elapsed
- That means the average speed of a trip is total distance of the trip
divided by the total time of the trip
- Total times means the time of the movement and breaks
* Lets solve the problem
- Gretel is traveling from Chicago to Atlanta
- Her average speed for the trip (including stops) is 60 mph
- She arrives at 10:00 pm
∵ The rule of average speed = total distance/total time
- Find the distance she traveled lets rearrange the formula
- Multiply the both sides of the formula by total time
∴ Total distance = average speed × total time
∵ average speed = 60 mph
∴ We need the total time
- The total time of her trip is the difference between the arrival time
and the departure time
∵ She arrives Atlanta at 10:00 pm
∴ We know the arrival time
∴ We need to know the departure time from Chicago
∴ The additional piece of information will allow us to determine how
far Gretel Traveled is the time she left Chicago