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Repeated part divisible by 9 (Posted on 2013-03-22) Difficulty: 2 of 5
Prove: if a rational number has a repeating decimal and the denominator is not divisible by 3 then the block of digits that repeats, taken as a decimal, is divisible by 9.

Examples:
7/13 = .538461 538461 538461 ...
538461 = 9*59829

15/22 = .6 81 81 81 ...
81 = 9*9

No Solution Yet Submitted by Jer    
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Comments: ( You must be logged in to post comments.)
  Subject Author Date
Some ThoughtsOther available conclusionsSteve Herman2013-03-24 10:28:57
Some Thoughtsthe simple waybroll2013-03-24 00:17:18
SolutionProof by geometric series (spoiler)Steve Herman2013-03-24 00:11:03
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