Correct Answer - Option 1 : 6

**Calculation:**

Let the numbers be 2y, 3y and 4y respectively.

⇒ (2y)^{2} + (3y)^{2} + (4y)^{2} = 261

⇒ 29y^{2} = 261

⇒ y^{2} = 9

⇒ y = 3

Greatest number = 4y = 12

Smallest number = 2y = 6

**∴ The difference between greatest number and smallest number is 6.**