(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Let m be a positive integer and m' be an integer obtained from m by rearranging its digits. Prove that m-m' is a multiple of 9

2. Relevant equations

Casting out 9's method

3. The attempt at a solution

So I found that by applying the casting out 9's method on m and m'; the values are the same. This means that when one divides m by 9 and m' by 9; it is the same remainder. I'm wondering how do I use this to prove that 9 divides m-m'

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# Homework Help: Modular arithmetic (casting out 9's)

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