courtesy Julius Sumner Miller

[essentialsaltes]

A man goes from A to B (which is any distance you please) uniformly at 30 miles per hour. ... At what rate must he return from B to A in order to average 60 miles per hour for the total journey?

Comments

[donovan k. loucks (from livejournal.com)]

Wow. That's amazing. The intuitive answer is 90 miles per hour. But I find the truth isn't as intuitive as we'd like it to be.

[johnny9fingers.livejournal.com]

If he travels 60 miles, it takes 2 hours at average 30mph. To return the 60 miles and average 60mph for both journeys would mean he needed to do it in no time at all.

Excellent. He'll need to book a Tardis for the return journey then.

[ladyeuthanasia.livejournal.com]

I am feeling mathematically inferior.