The difference of a number consisting of two digits from the number formed by interchanging the digits is always divisible by
let the digits of the no. be X and Y
number = 10x+y
reverse of no. = 10y+ x
now (10x+y) - (10y+x) = 9x-9y = 9(x-y)
as shown above that 9 will always be the factor, irrespective of the difference and the number
so it can be concluded that the resulting number will always be divisible by 9
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