2006-09-05 16:13:48 · 5 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
Add up all the digits in the number. If this sum is divisible by 3 then your original number is divisible by 3. You can sum up the digits of you sum again if you still have a large number.
i.e
36921
3+6+9+2+1 = 21
2+1 = 3
this is divisible by 3 therefore 36921 is divisible by 3
2006-09-05 16:17:09 · answer #1 · answered by Demiurge42 7 · 0⤊ 0⤋
Add the digits. If the sum is divisible by 3, the original number is divisible by 3.
For example:
Is 162 divisible by 3?
1 + 6 + 2 = 9
Since 9 is divisible by 3, 162 is divisible by 3.
2006-09-05 16:18:10 · answer #2 · answered by firemedicgm 4 · 0⤊ 0⤋
Add up all the seperate digits of the number. If the sum is divisible by 3, then the original number was also divisible by 3. The proof of it is very interesting, if you ever get the chance to read it.
2006-09-05 16:17:47 · answer #3 · answered by shyvurboie 4 · 0⤊ 0⤋
There's a rule?
2006-09-05 16:17:09 · answer #4 · answered by Anonymous · 0⤊ 0⤋
Yeah, what they said.
Schoolhouse Rock is flashing thru my head now..."Three...it's a magic number." ;)
2006-09-05 16:21:30 · answer #5 · answered by Tish 5 · 0⤊ 0⤋