On: The Rule of 72 (2007)

[archgoon]

This is taught in american middle schools and high schools. Multiple times; it's the defacto example of how exponents work.

It is not explicitly called out in the Common Core standard, but several of the examples in the common core are interest rate problems.

Here's an example from the California Standard, search for 'interest'.

http://www.cde.ca.gov/be/st/ss/documents/ccssmathstandardaug...

[sp332 → archgoon]

In addition, it's printed on my credit cards statements. There's a little box that prints the total time and total cost if I make minimum payments, and if I make payments that are some larger round number.