Question 29768: A WHOLE NUMBER IS DIVISIBLE BY 3, IF IT'S SUM IS DIVISIBLE BY 3..NOT SURE HOW TO DO THIS PLEASE HELP..
Answer by Cintchr(481)   (Show Source):
You can put this solution on YOUR website! This rule works for dividing by nine as well.
take the number 345. Add the digits up.
3 + 4 + 5 = 12
look at the answer ... 12. 12 is divisible by 3, so the number 345 is as well.
take a HUGE number .... 34,826,406,723,467
add the digits ...
3+4+8+2+6+4+0+6+7+2+3+4+6+7=62
we can now take 62 ... 6 + 2 = 8 .
3 can not go into 8 ... so it can not go into 34,826,406,723,467.
The same holds true with the number 9. but the sum of the numbers has to be divisible by 9.
85,716
8+5+7+1+6=27
9 goes into 27, so it goes into 85,716
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