The ratio of the radii of two circles is 1 : 3. Then the ratio of their areas is :

A. 1 : 3

B. 1 : 6

C. 1 : 9

D. None of these

Answer: Option C

Solution(By Examveda Team)

Let the radii of the two circle be r and 3r respectively.
Then, required ratio :
$$ = \frac{{\pi {r^2}}}{{\pi {{\left( {3r} \right)}^2}}} = \frac{{\pi {r^2}}}{{9\pi {r^2}}} = 1:9$$