AMO 2021 - Secondary 3 (Grade 9) Question 7

Question 7

A dart lands uniformly at random inside the larger circle $C_2$, whose diameter is 9 inches. The concentric shaded circle $C_1$ has diameter 3 inches. What is the probability of landing in $C_1$?

Question illustration

$1/3$
$1/4$
$1/6$
$1/9$
$1/\pi^2$