
Arundeep

DIVISIBILITY BY TWELVE : Rule : Any number which is divisible by both 4 and 3, is also divisible by 12.To check the divisibility by 12, we (1) first divide the last twodigit number by 4. If it is not divisible by 4, the number is not divisible by 12. If it is divisible by 4 then (2) check whether the number is divisible by 3 or not. Ex.1. 135792 : 92 is divisible by 4 and also (1+3+5+7+9+2=)27 is divisible by 3 ; hence the number is divisible by 12. Remark : Recall the method for calculation of digitsum. What did you do earlier "Forget nine". Do the same here. For example: digitsum of 135792__1 plus 3 plus 5 is 9, forget it. 7 plus 2 is 9, forget it. And finally we get nothing. That means all the "forget nine" counts a number which is multiple of 9. Thus, the number is divisible by 9. 