Saturday, May 9, 2009

Puzzle 4: Prove Divisibility Rule of 9

How to find out whether any given number is divisible by 9?
Most of you know. Just add all the digits in the number and
if the sum is divisible by 9 then entire number is divisible by 9.

The Question is how do you prove that mathematically?
Scratch your brain or wait for the solution in my next posting.

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