Answer:
If the area of the circle is 78.5 squared inches (note we use squared inches for areas and cubic inches for volume) and we want to know its radius 
 , we have to use the formula of the area of the circle:
, we have to use the formula of the area of the circle:
 
 
Then isolate 
 :
:
 
 
Applying square root on both sides:
 
 
 
 
Substituting the known values:
 
 
 >>>>>This is the radius
>>>>>This is the radius