John M. Flanigan <johnf@hawaii.edu> The equation is the final arbiter.
Math Resource Instructor --Werner Heisenberg
Kapi'olani Community College The scoreboard is the final arbiter.
Honolulu, Hawaii --Bill Walton
On Thu, 2 Oct 1997 CoolMath2@aol.com wrote:
> In a message dated 97-10-02 10:28:44 EDT, bgentry@PARKLAND.CC.IL.US writes:
>
> << A number is divisible by 7 IFF it satisfies the following:
> Subtract twice the right hand digit from the positive number represented
> by the remaining digits. If this difference is divisible by 7, then the
> original
> number is divisible by 7. Seems to me that it would be easier to use my
> calculator and divide by 7 to test for divisibility by 7. ;>) >>
>
> So Barb, what do you think of the divisibility (man, that's hard to type!)
> test for 11?
>
> Let's see if I can even describe it well ------
> Take the sum of the digits that are in places that are even powers of 10 and
> subtract the sum of the digits that are odd powers of 10. If the result is
> divisible by 11, then the original number is divisible by 11.
>
> I'd better give an example!
>
> Does 11 divide 28374957?
>
> (7+9+7+8) - (5+4+3+2) = 17 , 11 does not divide 17 so 11 does not divide
> that big number we started with! 8-)
>
> Karen
> Orange Coast College
> http://members.aol.com/coolmath2/coomath.htm
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