a quick math challenge

12292013, 02:19 PM
(This post was last modified: 12292013 02:20 PM by Waon Shinyoe.)
Post: #9




RE: a quick math challenge
(12282013 10:06 PM)Les_Koller Wrote: I teach 9th grade Alg 1, and am happy to report approx 80% of my students rember the 2, 3, and 5 rules. Cannot figure out why they can't remember the by 6 rule! Excuse me but what's the 2,3, and 5 rules? I think a 9digit number contains 1~9 can be divided by 3 because (abcdefghi) mod 3 = (1*9 + (0+1+2)*3 ) mod 3 = 18 mod 3 = 0 (I'm a high school student in P.R.China.) 

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