Circumference(c)= pi*diameter
if d=2.1 cm
then c= (22)(2.1)/7
if d=3.2cm
 then,  c=(22)(3.2)/7
           c=10.06 cm rounded off.
if d=4.5cm
     then, c=(22)(4.5)/7
             c=14.143 cm rounded off

"22/7 is not exactly a pi" even if you ask your instructor..
22/7 is not the final answer so we can't round off it. because your answer might be wrong..
the pi in the formula in getting circumference is a constant so we cant replace with the other constant..
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