Question

if the difference between a number and the number obtained by interchanging its digit is 45 what is the difference between the digit of that number

Answer 1

The difference will be 5 because, 9*5=45. It's because, the "difference between a number and the number obtained by interchanging its digits" is 9 times the "difference between the digit of that number."

P.S= This shortcut works only in case of 2 digit numbers.