A car travels 100 km at a speed of 50 km/h and then returns at 100 km/h. What is the average speed for the entire trip?
Category: Math · Difficulty: hard
Hint: Use the harmonic mean for average speed.
Answer
66.67 km/h
Explanation
Average speed = total distance / total time; total time = 2 hours + 1 hour = 3 hours; average speed = 200/3.
This is a hard math riddle — a tricky one that takes a little thought. The answer is 66.67 km/h.
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