Pick a two digit number with distinct digits. Now, reverse the digits. Subtract the smaller number from the larger number. The sum of the digits of the difference obtained is always ____.
9
Let the two digit number be 10A+B and its reverse will be 10B+A
Subtraction of these numbers would yield 9(A−B) or 9(B−A).
In either way, the number thus obtained will be multiple of 9 and the whole number is divisible by 9.
Therefore, the sum of all digits of the number should be 9 or multiple of 9.
The digits of the difference will be less than 9.Therefore, the sum of these digits will always be 9.