Correct Answer - Option 3 : 79

**Given:**

Sum of digits of number is 16

**Concept used:**

When digits of a number gets interchanged, the unit place becomes the tens place and vice versa

**Calculation:**

Let the original number be (10x + y)

Now, A/Q

⇒ 10x + y + 18 = 10y + x

⇒ 9y – 9x = 18

⇒ y – x = 2 ----(1)

And x + y = 16 ----(2)

Adding equation(1) and (2)

⇒ 2y = 18

⇒ y = 9

From equation (1)

⇒ x = 7

**∴ The original number is 79**