the picture in the attached figure
step 1
find the area of a square
area of a square=b²
b in this problem is the diameter of a circle
b=2*9------> b=18 units²
area of a square=18²-----> 324 units²
step 2
find the area of a circle
area of a circle=pi*r²
r=9 units
area of a circle=pi*9²------> 254.34 units²
step 3
find the probability that the dart hits a point in the circle
P=area of the circle/area of the square
P=254.34/324------> P=0.785-----> 78.5%
the answer is
78.5%
