Prove that if n is a positive integer such that the sum of the digits of n in decimal representation is divisible by 3 then n is divisible by 3
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Originally Posted by mandy123 Prove that if n is a positive integer such that the sum of the digits of n in decimal representation is divisible by 3 then n is divisible by 3 This one is sort of the archetype for the rest of them. Note that for all positive n. So putting a number x into its decimal representation in base 10: We see that So if (ie. the sum of the digits of x is divisible by 3), then the number x is divisible by 3. -Dan
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