Question 259699
In general, the area of a circle is
{{{A=pi*r^2}}}
and the circumference is
{{{C=2*pi*r}}}
Then
{{{A/C=pi*r^2/(2*pi*r)}}}
{{{A/C=r/2}}}
Since 
{{{D=2r}}}
{{{r/2=D/4}}}
{{{A/C=D/4=4/4=1}}}