Tuesday, June 21, 2011

Link of the Day: The Rule of 72

Not a lot of time, but this post took me back in time.

First, I learned about the Rule of 72 from my uncle, back in the
days of double-digit interest rates. It was a quick way of figuring
out when an investment was expected to double. Conversely, you could
use it to figure out how long it would take for the amount you owe
your credit company to double as well, if you couldn't pay it off.
At the time I remembered the Taylor expansion of e (or is it the
Maclaurin expansion), and could derive why this worked.

About ten years later I met Terry Jones at Indiana U, learned how to
bounce five balls (and why bouncing five balls looked so much better
than the much harder accomplishment of keeping seven balls in the air).
Terry soon after left the 80s-era computer science of Hofstadter's
office for the emerging, cooler complexity theory of Santa Fe,
and now runs a startup in NYC.

And today I was pointed to his post yesterday about the rule of 72.
Go read it, and amaze or bore your less financially literate buds.


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