“Few people, including many mathematicians, know all the simple rules by which large numbers can be tested quickly for divisibility by numbers 1 through 12,” Gardner remarked ...

(3) To check for divisibility of 8976730213 by 11 ... As 0 is divisible by 11, so is the number 8976730213. (8976730213 = 11 × 816066383). Now you can apply the concept to solve the toughest ...

The second problem is of the form that you may encounter in CAT. We know from divisibility rules that for any five digit number to be a multiple of 11, if the number is of the form: abcde ...