**Let the radii of the given circles be 4x and 5x respectively and let their areas be A**_{1} and A_{2} respectively.

Then, A_{1 }= πr^{2}

= A_{1} = π × (4x)^{2}

= A_{1 }= 16πx^{2}

And A_{2 }= πr^{2}

= A_{2 }= π × (5x)^{2}

= A_{2} = 25πx^{2}

∴ (A_{1}/A_{2}) = (16πx^{2})/ (25πx^{2})

(A_{1}/A_{2}) = (16/25)

A_{1}: A_{2} = 16: 25

**Hence, the ratio of the areas of two circles is 16: 25**