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**ZHero****Real Member**- Registered: 2008-06-08
- Posts: 1,889

I am interested to know that "what is the probability that a number chosen at random will have the sum of its digits divisible by 9"?

Plz help...

If two or more thoughts intersect, there has to be a point!

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**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

Robert Ward wrote:

Numerals whose sum of digits is divisible by 9 represent numbers divisible by 9 and vice versa

The set S = {9,18,27,36,45,54,...} are all divisible by 9 and the sum of their digits is divisible by 9:

Every ninth number is divisible by 9 and has the sum of the digits divisible by nine. So:

P(n | 9 and sum of the digits of n is | 9) = 1 / 9 or 8 to 1 against.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

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**ZHero****Real Member**- Registered: 2008-06-08
- Posts: 1,889

That was easy! I was wondering about Prime numbers when a question arose in my mind... now i realize that this one was of no help.

If two or more thoughts intersect, there has to be a point!

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