The ratio of the radii of two circle is 1:3 the radio

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The ratio of the radii of two circle is 1:3 the radio of their areas is?

1. 1:3
2. 1:6
3. 1:9
4. None of these

Correct Option: C

The Radio of areas = area of first circle : area of 2nd circle
= πr² / π(3r)²
= πr²/ 9 πr²
= 1/9
= 1: 9