10 km/h 20 km/h 40 km/h 50 km/h
I gave my students this multiple choice question: In one day, a family in a car rode for 2 hours, stopped for 3 hours, and then rode for another 5 hours. During the day, the family traveled a total distance of 400 kilometers. What was their average speed for the whole trip?

Only one answer is correct among these 4 choices:
- 10 km/h
- 20 km/h
- 40 km/h
- 50 km/h

Could you tell me which one is correct?

40 km/h