Correct Answer - Option 3 : m ∶ n

^{2}
**Given:**

Ratio of area of two squares = m^{2} ∶ n^{4}

**Formula used:**

Area of square = (side)^{2}

Perimeter of square = 4 × (side)

**Calculation:**

As we know that

Area of square = (side)^{2}

Area of Square_{1} = m^{2} = (side_{1})^{2}

⇒ m = side_{1}

And, Area of Square_{2} = n^{4} = (side_{2})^{2}

⇒ (n^{2})^{2} = (side_{2})^{2}

⇒ n^{2} = side_{2}

Now,

The ratio of Perimeters = Perimeter of Square_{1} ∶ Perimeter of Square_{2}

⇒ (4 × side_{1}) ∶ (4 × side_{2})

⇒ m ∶ n^{2}

**∴ The ratio of their perimeters is m ∶ n**^{2}.