Question

The sum of the digits of a two-digit number is 9. If the digits are reversed,the new number is 9 more than the original number.Find the original number.

Answer 1

45

Explanation:

Let the original number be xy where y is unit and x is tens hence original number is 10x+y When reversed, the new number is yz hence 10y+x

We know that the original number plus 9 is the reversed number hence

10x+y+9=10y+x

9y-9x=9 which when simplified we obtain that

y-x=1 equation 1

Originally, we are told that the sum of x and y is 9 hence

y+x=9 equation 2

Solving equation 1, it means y=x+1

Substituting the above into equation 2

x+1+x=9

2x=9-1

2x=8

x=8/2=4

Since y=x+1 then y=4+1=5

Therefore, the original number, xy is 45