Answer:
16/5 or 3 1/5
Step-by-step explanation:
Your equation would be 4/5*4 which equals 16/5
 
        
             
        
        
        
Please note that pi has just one value.  The only difference stems from round-off error when you don't use all of the digits following "3.14159 ... " to represent the value of pi.  The formula for circumference is C = 2 pi r, or C = pi d, 
where r=radius and d=diameter.
Circle A:  Diameter 9 inches and Circumference of 28.26 inches
If the diameter is 9 inches, then C = 28.26 inches = pi (9 inches).  Divide 28.26 inches by 9 inches.  Note that you MUST round off the ratio (pi) that you obtain, since 28.26 has 4 significant figures and 9 has just one.
28.26
------- = 3.14, but because 9 has just one significant figure, you must round 
    9           this 3.14 to just 3.