Question

In the given question, fill in the blanks to make the statement true.

The difference of a two-digit number and the number obtained by reversing its digits is always divisible by ___.

Answer 1

9
Let ab be any two-digit number, then we have
ab - ba = (10a + b) - (10b + a)
= 9a - 9b
= 9(a - b)
Hence, ab - ba is always divisible by 9 and (a - b).