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| From | Sегgi о <iinvalid@invalid.com> |
|---|---|
| Newsgroups | sci.math, sci.physics, alt.astronomy |
| Subject | Re: The Rule Of 72 |
| Date | 2017-06-19 08:45 -0500 |
| Organization | Aioe.org NNTP Server |
| Message-ID | <oi8khs$1v7s$1@gioia.aioe.org> (permalink) |
| References | (16 earlier) <oi5q6q$1oip$1@gioia.aioe.org> <PM0005523BFFEC5FCC@aca43d4d.ipt.aol.com> <oi6hiq$2p5$1@dont-email.me> <oi6jm9$vre$1@gioia.aioe.org> <PM0005524F9D7B2F8F@aca4299c.ipt.aol.com> |
Cross-posted to 3 groups.
On 6/19/2017 7:43 AM, jmfbahciv wrote: > Sегgi о wrote: >> On 6/18/2017 1:42 PM, Jack Fearnley wrote: >>> On Sun, 18 Jun 2017 13:21:35 +0000, jmfbahciv wrote: >>> >>> >>>> But it's a fast way to estimate the time to double the original amount >>>> when the interest or dividends are reinvested. >>>> >>>> IIRC, divide 72 by the percentage. That will give the number of year to >>>> double the original amount. >>>> >>>> /BAH >> >>> The exact doubling time is log(2)/log(1+r/100). >>> If we expand log in a Taylor series and take only the first term >>> we get the approximate doubling time as 100*log(2)/r. >>> That is 69.315/r. >>> So why don't we use a rule of 69 or a rule of 70? >>> >>> It turns out that, in the range 1% to 10% and rounded to whole years, 72 >>> is more accurate than 69.315. >>> >>> I found this quite surprising. >>> >>> Best regards, >>> Jack Fearnley >>> >> >> >> >> I got this confused with the Rule of 78 used with Loans, >> >> http://www.tiac.net/~mabaker/rule_of_78.html >> >> it replaced simple interest calculation in the 60's and 70's and >> it made you pay more for a loan > > I don't remember loans ever being simple interest. > > /BAH > I think it is dependent upon which state you are in, here the "rule of 78" was discontinued from home loans. But I think that in other states it is still legal.
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The Rule Of 72 The Starmaker <starmaker@ix.netcom.com> - 2017-06-16 10:27 -0700
Re: The Rule Of 72 Dan Christensen <Dan_Christensen@sympatico.ca> - 2017-06-16 11:05 -0700
Re: The Rule Of 72 William Elliot <marsh@panix.com> - 2017-06-18 00:46 -0700
Re: The Rule Of 72 Sегgi о <iinvalid@invalid.com> - 2017-06-18 07:03 -0500
Re: The Rule Of 72 jmfbahciv <See.above@aol.com> - 2017-06-18 13:21 +0000
Re: The Rule Of 72 Jack Fearnley <jack@alcor.concordia.ca> - 2017-06-18 18:42 +0000
Re: The Rule Of 72 Sегgi о <iinvalid@invalid.com> - 2017-06-18 14:18 -0500
Re: The Rule Of 72 jmfbahciv <See.above@aol.com> - 2017-06-19 12:43 +0000
Re: The Rule Of 72 Sегgi о <iinvalid@invalid.com> - 2017-06-19 08:45 -0500
Re: The Rule Of 72 jmfbahciv <See.above@aol.com> - 2017-06-20 12:12 +0000
Re: The Rule Of 72 jmfbahciv <See.above@aol.com> - 2017-06-19 12:43 +0000
Re: The Rule Of 72 The Starmaker <starmaker@ix.netcom.com> - 2017-06-19 10:46 -0700
Re: The Rule Of 72 The Starmaker <starmaker@ix.netcom.com> - 2017-06-19 20:01 -0700
Re: The Rule Of 72 jmfbahciv <See.above@aol.com> - 2017-06-20 12:12 +0000
Re: The Rule Of 72 The Starmaker <starmaker@ix.netcom.com> - 2017-06-20 07:28 -0700
Re: The Rule Of 72 jmfbahciv <See.above@aol.com> - 2017-06-21 12:54 +0000
Re: The Rule Of 72 The Starmaker <starmaker@ix.netcom.com> - 2017-06-21 12:19 -0700
Re: The Rule Of 72 jmfbahciv <See.above@aol.com> - 2017-06-22 12:28 +0000
Re: The Rule Of 72 The Starmaker <starmaker@ix.netcom.com> - 2017-06-22 08:58 -0700
Re: The Rule Of 72 jmfbahciv <See.above@aol.com> - 2017-06-23 11:40 +0000
Re: The Rule Of 72 The Starmaker <starmaker@ix.netcom.com> - 2017-06-23 10:11 -0700
Re: The Rule Of 72 jmfbahciv <See.above@aol.com> - 2017-06-24 11:40 +0000
Re: The Rule Of 72 The Starmaker <starmaker@ix.netcom.com> - 2017-06-24 09:12 -0700
Re: The Rule Of 72 jmfbahciv <See.above@aol.com> - 2017-06-25 13:50 +0000
Re: The Rule Of 72 Jack Fearnley <jack@alcor.concordia.ca> - 2017-06-20 14:54 +0000
Re: The Rule Of 72 jmfbahciv <See.above@aol.com> - 2017-06-21 12:54 +0000
Re: The Rule Of 72 djheydt@kithrup.com (Dorothy J Heydt) - 2017-06-18 14:07 +0000
Re: The Rule Of 72 David Bernier <david250@videotron.ca> - 2017-06-18 12:38 -0400
Re: The Rule Of 72 djheydt@kithrup.com (Dorothy J Heydt) - 2017-06-18 19:27 +0000
Re: The Rule Of 72 "hanson" <hanson@quick.net> - 2017-06-18 16:07 -0700
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