Question

The sum of a two-digit number and the number obtained by reversing the order of its digits is 121, and the two digits differ by 3. Find the number.

Answer 1

Let x be the ones digit and y be the tens digit. Then 

Two digit number before reversing = 10y + x 

Two digit number after reversing = 10x + y 

As per the question (10y + x) + (10x + y) = 121 

⇒11x + 11y = 121 

⇒x + y = 11 …….(i) 

Since the digits differ by 3, so 

x – y = 3 ……….(ii) 

Adding (i) and (ii), we get 

2x = 14 

⇒ x = 7 

Putting x = 7 in (i), we get 

7 + y = 11 

⇒ y = 4 

Changing the role of x and y, x = 4 and y = 7 

Hence, the two-digit number is 74 or 47.