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Topic: Great Math Tricks on youtube
Replies: 8   Last Post: Jan 1, 2014 9:36 AM

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Thomas Nordhaus

Posts: 433
Registered: 12/13/04
Re: Great Math Tricks on youtube
Posted: Jan 1, 2014 9:36 AM
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Am 01.01.2014 01:31, schrieb Christopher J. Henrich:
> In article <79fe4482-109f-4177-b73a-eee98fa1dff8@googlegroups.com>,
> christian.bau <christian.bau@cbau.wanadoo.co.uk> wrote:

>> On Monday, December 30, 2013 8:37:29 AM UTC, Phil Carmody wrote:
>>> Today I learnt that
>>> 11.5 / 2 = 6.725
>>> Teach me more of these internet things called "math tricks"!

>> Sad that the guy is really bad at mental arithmetic.
>> Apart from that, he tells us that to solve (1 + p / 100)^n = 2 for n we let n
>> = 72 / p,

> A better approximation is 69/p, based on ln(2) = 0.693...

Of course this is a better approximation for very small values of p, but
they are not of very high interest for an investor ;) For values of p
between let's say p=5% and p=20% the 72-rule seems to work better.

Thomas Nordhaus

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