Road Trip
You're on a road trip with your friends. From the start, you drive with an average speed of 50 miles/hour for 6 hours before stopping to have lunch at a diner place for 1 hour.
Then you continue your journey with an average speed of 70 miles/hour for the next 5 hours before reaching downtown and stopping for a supper for 1 hour.
Afterwards, the traffic jam is so bad that you can only use an average speed of 20 miles/hour for 2 hours to arrive at the final destination.
What is the average speed of the whole road trip in miles/hour?
The answer is 46.
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1 solution
Average speed = Total time traveled Total distance traveled .
The total distance = 5 0 × 6 + 7 0 × 5 + 2 0 × 2 = 300 + 350 +40 = 690 miles.
The total time = 6 + 1 + 5 + 1 + 2 = 15 hours.
Thus, the average speed = 690/15 = 46 miles/hour.