The formula of an area of a circle:

We have
r = 1.8 m
π ≈ 3.14
Substitute:

x = 6
given f(x) = 310, we obtain the equation
10 + 50x = 310 ( subtract 10 from both sides )
50x = 300 ( divide both sides by 50 )
x =
= 6
This equals the the area of white part / area of the entire dartboard
area of the entire board = pi * 6^2 = 36pi
area of white part = 36pi - 2^2*pi = 32pi
do required probability = 32pi / 36pi = 0.889 or 88.9 % (to nearest tenth)
or as a fraction it is 8/9
Answer
<span>C. root 3 + 8.486</span>