Question

If a two digit number difference is by 7 if the digits are interchanged and the resulting number is added to the original number we get 121 find the original number

Answer 1

Let the two digit number be 10x + y.
By the problem,
x - y = 7...(1)

Also,
10y +x + 10x + y = 121
=>11x +11y = 121
=> x + y = 11.... (2)

Adding (1) and (2), we get
2x = 18
=> x =9

Substituting the value of x in (1)
9 - y =7
=>y =2

The required two digit number
= 10(9)+2
=92(ans)

Hope this helps :)