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From Rob Weir <robw...@apache.org>
Subject Re: Calc: Easy way to do N+(N-1)+(N-2)+(N-3)..(N-N+1)
Date Sat, 22 Jun 2013 14:53:57 GMT
On Fri, Jun 21, 2013 at 6:39 PM, Toki Kantoor <toki.kantoor@gmail.com> wrote:
> On 06/21/2013 06:37 PM, Brian Barker wrote:
>> Yes.  Sigma (1 to n) is n(n+1)/2.
>
> Thanks.
>
>>> If so, what is the formula, extension, or something?
>>
>> =Xn*(Xn+1)/2
>>
>> I trust this helps.
>
> It helps a lot.


There is a famous story about this formula.  The mathematician Carl
Friedrich Gauss, when he was 10 years old, was in an arithmetic class
where the teacher gave them all the problem to sum the digits from 1
to 100.

Maybe the teacher had some other task he wanted to do, or wanted to
take a nap?  So he gave them this task to keep them busy.

Gauss figured this out in his head (the answer is 5050), by
discovering the above formula, and put down his slate, much angering
the teacher.

The key is to rearrange the calculation.  So instead of
1+2+3+4...+100, think of it as: (1+100) + (2+99) + (3+98) ... +
(49+52) + (50+51) = 101*50

Regards,

-Rob

> I wish I had book that contained functions and their formula, that
> somebody that never took a match course could understand.
>
> jonathon
> --
> LibreOffice in a Multi-Lingual Environment.
>
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