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Old 08-28-2016, 01:02 PM
Leo Bloom Leo Bloom is offline
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Join Date: Jun 2009
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"Casting out nines": Wolfram Math: http://mathworld.wolfram.com/CastingOutNines.html


For a mess of them:
"Divisibility tests": Wolfram Math: http://mathworld.wolfram.com/DivisibilityTests.html

Last edited by Leo Bloom; 08-28-2016 at 01:02 PM.