Quote:
Originally Posted by island911
one good trick is that if the numbers in the number add up to 3, then it is also divisible by 3.
example: 123 .. . . 1+2+3=6 (=>divisible by 3)
anything divisible by 5 is obvious. Same for 2.
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And how does that work for the example he listed: 28 and 84, or 46 and 138?