Aptitude Hack#137(10-7-19)

Question:

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) 5.

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