Answer
a). The radius is 16.5m
b). The circumference is 103.67m
c). They would have to be 3.5m apart
d). The co-ordinates of the circle are (0,4.062) with radius 16.5m
e). $x^2 + (y-4.062)^2=16.5$
Work Step by Step
a). The radius of a circle is half its diameter, so $r=\frac{d}{2}=16.5m$
b). The formula for the circumference of a circle is $C=2 \pi r =2 \pi \times 16.5m=103.67m$
c). Divide the circumference the circle by the number of stones: $\frac{103.67}{30}=3.5m$
d). We can plot the equation $x^2 + (y-4.062)^2=16.5$ to get the same circle as the one given in the question.
e). See the graph in the attachment, it's equation is $x^2 + (y-4.062)^2=16.5$
