'ABC' is a 3 digit number if it is reversed then the sum of digits of the difference between the original and the reversed number will always be divisible by:
All of these
ABC can be written as 100A+10B+C
Similarly CBA can be written as
100C+10B+A
ABC−CBA=(100A+10B+C)−(100C+10B+A)
=100A+10B+C−100C−10B−A
=99(A−C)
=9×11(A−C)=3×3×11(A−C)
This number is divisible by 3,9,11 and 99.
If a number is divisible by 9 and 3, the sum of the digits of that number must be divisible by 9 and 3 respectively.