Brainteasers
Brainteaser – Round Trip Riddle
If you take a journey (the same distance in both directions) and average 70 mph on your way out, but only 50 mph on your return trip…
What is your average speed for the entire trip?
Show Answer
58+1/3 mph.
The catch here is that the constant is distance rather than time. So we can choose an arbitrary distance (as distance doesn’t matter, e.g. 350 miles each way).
350 miles @ 70mph takes 5 hours
350 miles @ 50mph takes 7 hours
Therefore 700 miles (total trip) takes 12 hours.
Average speed = 700 / 12 = 58.333′
