Wednesday, December 14, 2011

Rule for 7

Take the last digit in a number.

Double and subtract the last digit in your number from the rest of the digits.

Repeat the process for larger numbers.

Example: 357 (Double the 7 to get 14. Subtract 14 from 35 to get 21 which is divisible by 7 and

we can now say that 357 is divisible by 7.


  1. does it work on all numbers ?

  2. your post looks like skittles