Dividing By Nine
The trick for determining if a number is divisible by nine is well-known: If the sum of the digits of a number is divisible by nine, then the number itself is as well. This is a special case of the general rule, made easy because no base conversion is necessary since 9 + 1 = 10, and we already use base 10.
Example: Is 2,340 divisible by 9?
- a=9
- b=2,340
- x=a+1=10
- y=b (base-10)=2,340
- z=2+3+4+0=9
- z/a=9/9=1, a natural number
2,340 is divisible by 9.
Read more about this topic: Base Conversion Divisibility Test
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