The difference between a two-digit number and the number obtained by interchanging the positions of its digits is 45. What is the difference between the two digits of that number?
(A) 5
(B) 7
(C) 6
(D) None of these


Answer: (A)

Explanation:

Let the ten’s digit be x and unit’s digit be y
Then (10x + y) – (10y + x) = 45
         9(x – y) = 45
           x – y = 5

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