perplexus.info :: Just Math : Nine forever

Nine forever (Posted on 2015-09-30)

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)	Jer	2015-09-30 17:32:16
Aha! (spoiler)	Steve Herman	2015-09-30 14:59:06

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