Re: Subtract Hours From A Given Date

A copy of this was sent to Kenneth C Stahl <BlueSax_at_Unforgettable.com> (if that email address didn't require changing) On Mon, 13 Sep 1999 07:50:09 -0400, you wrote:

>Thomas Kyte wrote:
>

[snip]

>> >
>> >10/1440 is a rational number....
>> >0.006944444444444........ (lots of 4's) is not.
>> >
>>
>> Wait a minute. I had to run home and get my old high school text book out :)
>>
>> 10/1440 is rational
>> AND SO IS 0.006944444444444........ (lots of 4's)
>>
>> (and so is 5/24) -- in fact every number that can be represented as X/Y is
>> rational. 10/1440 is a repeating number but it is not irrational.
>>
>> Not that is matters.....
>>
>> [snip]
>>

>I would believe you if you could be given the number of 0.2083333333333 and work
>backwards to determine that it is the ratio of 5/24 - I suspect that isn't possible.
>

Don't believe me. Believe the high school text book description of a rational number. You can find a very simple one at:

http://www.utm.edu/research/primes/glossary/RationalNumber.html

Part of the definition is:

<quote>
The rational numbers are those which have repeating decimal expansions (for example 1/11=0.09090909..., and 1=1.000000...=0.999999...). </quote>

So -- any number that repeats is rational. .20833333333 (repeating 3) is a great example of a repeating number. Numbers such as PI, sqrt(2) and 'e' are examples of numbers that do no repeat and are irrational.

>I'm trying to get some clarification from my wife on this. She knows far more about the
>subject than I do since she has a degree in Math.
>

--
See http://govt.us.oracle.com/~tkyte/ for my columns 'Digging-in to Oracle8i'... Current article is "Part I of V, Autonomous Transactions" updated June 21'st  

Thomas Kyte                   tkyte_at_us.oracle.com
Oracle Service Industries     Reston, VA   USA

Opinions are mine and do not necessarily reflect those of Oracle Corporation Received on Mon Sep 13 1999 - 08:08:18 CDT