The Math Forum

Search All of the Math Forum:

Views expressed in these public forums are not endorsed by NCTM or The Math Forum.

Math Forum » Discussions » sci.math.* » sci.math

Notice: We are no longer accepting new posts, but the forums will continue to be readable.

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

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]
Thomas Nordhaus

Posts: 433
Registered: 12/13/04
Re: Great Math Tricks on youtube
Posted: Jan 1, 2014 9:36 AM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

Am 01.01.2014 01:31, schrieb Christopher J. Henrich:
> In article <>,
> christian.bau <> 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

Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© The Math Forum at NCTM 1994-2018. All Rights Reserved.