A traveler drives up a mountain road at 30 miles per hour, then turns right around and returns down the exact same road at 60 miles per hour. What was the traveler's average speed for the whole round trip?
40 mph
Average speed is total distance divided by total time. For distance d, time up is d/30 and time down is d/60. Total time = 3d/60 = d/20. Total distance = 2d. Average speed = 2d / (d/20) = 40 mph.
About this riddle
Math riddles hide a calculation inside a short story. Pull out the numbers, work out what is being asked, and watch for a trick such as a unit change.
Difficulty: Hard. More like this: Math riddles with answers or try Target 24 for a different kind of puzzle.
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