[Retric]

The issue is he then uses the approximations to do with math without calling them approximations. 1.10^7 is reasonably close to 2, but 1.1^21 is 7.4 which is a fair distance from 8.

He goes so far as asks someone to do the approximation across several hundred years of compounding. And sure it get’s a big number but one no even close to accurate.

[Loanor]

You do realize the rule of 70 is used to approximate continuous compounding not periodic compounding right?

[Retric]

There are a bunch of them though compounding normally uses the rule of 69 / 69.3, or rule 72. https://en.wikipedia.org/wiki/Rule_of_72