Question

The sum of the digits of a two digit number is 7. If we interchange the digits, then the resulting number is 9 less than the original number, then what is the digit?​

Answer 1

Answer:

Let the digit at tens place be x then digit at ones place will be (9-x).

Original two digit number = 10x + (9-x)

After interchanging the digits, the new number = 10(9-x) + x

According to the question,

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

⇒ 10x + 9 - x + 27 = 90 - 10x + x

⇒ 9x

+36 = 90 - 9x

⇒ 9x + 9x = 90 - 36

⇒ 18x = 54

⇒ x = 3

Original number = 10x + (9-x) = (10×3) + (9-3) = 30 + 6 = 36

Thus, the number is 36.

Answer 2

The digit is 43.

4 + 3 = 7

If we interchange the digits of 43, we get 34, that is 9 less than 43.