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Nine forever (Posted on 2015-09-30) Difficulty: 3 of 5
Prove that if the digits of N, read from left to right, form a strictly increasing sequence, the sum of the digits of 9*N is always 9 (nine).

You are requested to formally prove, not to verify.

No Solution Yet Submitted by Ady TZIDON    
Rating: 4.0000 (1 votes)

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  Subject Author Date
re: Aha! (spoiler)Jer2015-09-30 17:32:16
SolutionAha! (spoiler)Steve Herman2015-09-30 14:59:06
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