Question

The sum of digit of a two-digit number is 9. if the digit are reversed, the new number will be 9 more than original number. find the original number

Answer 1

Let’s say x is the unit digit and y is the tenth digit.

y+x = 9 -> y=9-x

10x+y = 10y+x+27

10x+9-x = 10(9-x)+x+27

10x+9-x = 90–10x+x+27

18x = 108

x = 6

so y = 3

let’s check

63 - 39 =27

27 = 27 (correct)